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Title: A Conchological Manual
Author: Sowerby, George Brettingham, 1788-1854
Language: English
As this book started as an ASCII text book there are no pictures available.
Copyright Status: Not copyrighted in the United States. If you live elsewhere check the laws of your country before downloading this ebook. See comments about copyright issues at end of book.

*** Start of this Doctrine Publishing Corporation Digital Book "A Conchological Manual" ***

This book is indexed by ISYS Web Indexing system to allow the reader find any word or number within the document.



Transcriber's note: A few typographical errors have been corrected: they
are listed at the end of the text.

       *       *       *       *       *


[Illustration]

  1. _Spondylus Americanus. (Young.)_

  2. _Nautilus pompilius. (Young.)_

                            _G. B. S. Jun^r. fecit._

       *       *       *       *       *


A

CONCHOLOGICAL MANUAL.

BY

G. B. SOWERBY, JUN.

ILLUSTRATED BY UPWARDS OF SIX HUNDRED AND SIXTY FIGURES

       *       *       *       *       *

SECOND EDITION.

CONSIDERABLY ENLARGED AND IMPROVED.

       *       *       *       *       *

LONDON:

HENRY G. BOHN, YORK STREET, COVENT GARDEN.

MDCCCXLII.

       *       *       *       *       *


PREFACE TO THE FIRST EDITION.

It may be necessary in introducing this little volume, to state, that it is
strictly conchological, and that it is compiled for the use not only of
those who wish to acquire an elementary acquaintance with the subject, but
also of authors and others, who, desirous of extending their knowledge and
pursuing their researches, require a book of reference, containing a
general outline of what has been done by those who have trodden the same
path before them. It has been thought advisable, for general convenience,
to arrange the principal part of the information in alphabetical order:
adding tables of the systems of Lamarck and De Blainville, to facilitate
the systematic pursuit of the science.

Persons of the class first alluded to, will find great assistance in the
explanation of technical words, their application being further
illustrated, in most cases, by a reference to the figures; and, although
they might have been multiplied, it is trusted that enough are given for
every useful purpose.

The definition of the Classes, Orders, Families, and Genera, in the system
of De Blainville, and a tabular view, are presented for the use of those
who prefer it, or who wish to compare it with that of Lamarck.

In the explanation of the figures, will be found a systematic arrangement
of shells, according to Lamarck, including the names of genera established
or proposed since the publication of his system. The descriptions of
established genera have been rendered as concise and clear as possible. It
is hoped that no essential characters are omitted, and that those living
authors, whose proposed generic distinctions have been passed over in a few
words, will not have to complain of want of justice in the attempt to
interpret their meaning.

In most cases the generic name will be found accompanied by its derivation.
This has been done, in the hope of assisting the memory by associating the
meaning of a term with some peculiarity in the thing described. At the end
of each description of a genus, some general observations occur, pointing
out the principal character which distinguishes it from others, to which it
is nearly allied; and also stating the geographical or geological
distribution and habits of the animal.

The above descriptions and definitions are illustrated by a series of
plates, containing above 500 etchings of nearly as many proposed or
established genera, arranged in Lamarckian order, so as to show at a glance
all the generic forms of each family. And, although from their number, they
could not be very highly finished, it is hoped that they will be found
characteristic.

The compiler cannot replace his pen without acknowledging, with filial
gratitude, the kind assistance of one who has sacrificed much of his time
in bringing his knowledge and experience to bear upon the correctness and
utility of this humble attempt to remove some of the difficulties to which
the commencement of this, as well as of every other study, is exposed.

PREFACE TO THE SECOND EDITION

The favourable reception and rapid sale of the first edition of the
Conchological Manual having rendered a second necessary, the Author takes
this opportunity of explaining the nature of the alterations which have
been made. In doing this, he has to thank his friends for their
suggestions, which, together with his own increased knowledge and
experience, enable him to present a more complete and satisfactory work to
the scientific public.

For the further convenience of those who are studying the rudiments of the
science, an entirely new Introduction is given, in which, commencing with
the structure and gradual developement of the shell, the author has
endeavoured to explain the general principles of Conchology in systematical
order. This Introduction is illustrated by 100 wood-cuts, which will be
found greatly to assist the Student.

The definitions have been rendered more full and complete than before, and
the Author has profited by some manuscript notes communicated by a
scientific friend, to whom he desires to present his humble
acknowledgments. Upwards of four hundred explanations have been given of
words which did not appear in the former edition, three-fourths of which
are of generic and subgeneric names.

A large number of notes, referring to the geographical distribution of the
genera, have been added from the pen of Mr. G. B. Sowerby, Senior.

The plates have been carefully improved; and three, containing upwards of
eighty figures, have been added.

On the whole, it will be found that the amount of matter has been nearly
doubled; all the defects, as far as they have been discovered, have been
removed, and every means used of making the present edition as useful as
possible.

       *       *       *       *       *

NAMES OF AUTHORS ABBREVIATED.

    _Adans._ Adanson. Author of "Voyages du Senegal."

    _Bl._ Blainville. Author of "Manuel de Malacologie et de
    Conchyliologie," &c.

    _Brod._ W. J. Broderip, Esq. Author of various descriptions of Shells
    in the Zoological Journal, &c.

    _Brongn._ Brongniart. Author of "Memoire sur les terrains du Vicentin,
    d'Italie, de France, et d'Allemagne," &c.

    _Brug._ Brugière. Author of "Dictionaire des Vers testacés, dans
    l'Encyclopédie," &c.

    _Cuv._ The late Baron Cuvier. Author of "Regne Animal," &c.

    _Defr._ Defrance. Contributor to the "Annales des Sciences Naturelles,"
    &c.

    _Desh._ Deshayes. Author of "Coquilles fossiles des environs de Paris,"
    &c.

    _D'Orb._ D'Alcide D'Orbigny.

    _Drap._ Draparnaud. Author of "Histoire Naturelle des Mollusques
    terrestres et fluviatiles de la France," &c.

    _Fer._ De Ferussac. Author of "Histoire Naturelle des Mollusques
    terrestres et fluviatiles," &c.

    _Flem._ Fleming.

    _Gmel._ Gmelin. Author of an edition of Linnæus's "Systema Naturæ," &c.

    _Guild._ Rev. Lansdown Guilding.

    _Hübn._ Hübner.

    _Humph._ The late George Humphrey.

    _Lam._ Lamarck. Author of "Animaux sans Vertebres," &c.

    _Lin._ Linnæus. Author of "Systema Naturæ," &c.

    _Mont._ Montague. Author of "Testacea Britannica," &c.

    _Montf._ Montfort. Author of "Histoire Naturelle des Mollusques," &c.

    _Müll._ Müller. Author of "Vermium terrestrium et fluviatilum,"
    "Zoologiæ Danicæ," &c.

    _Ranz._ Ranzani. Author of "Considerations sur les Balanes," &c.

    _Schum._ Schumacher.

    _Sow._ Sowerby. The late James. Author of "Mineral Conchology," &c.
    George Brettingham, Senr., "Genera of Shells," "Species Conchyliorum,"
    &c. G. B. Jun. "Conchological Manual," "Conchological Illustrations,"
    "Thesaurus Conchyliorum," Descriptions of New Shells in the Zoological
    Proceedings, &c.

    _Sw._ Swainson. Author of "Zoological Illustrations," "Exotic
    Conchology," "Lardner's Cabinet Cyclopedia," &c.

    _Turt._ Turton. Author of "British Shells."

       *       *       *       *       *


INTRODUCTION.

The Science of Conchology affords a very delightful and instructive
amusement for the leisure hours of those who, retiring occasionally from
the gaieties of fashionable life, seek pleasure in the quiet contemplation
of some of the smaller, but not less wonderful operations of creative
wisdom. And, although the study of shells would be more complete, and rank
higher in the scale of philosophical pursuits, were it always accompanied
by that of the animal inhabiting them, it nevertheless presents means of
intellectual gratification, to many who cannot follow it beyond the cabinet
and the boudoir. These may examine with admiration and mental improvement,
the beautiful colouring and architecture of these wonders of the deep, they
may exercise their taste and judgment in the selection and arrangement of
specimens, and their discrimination in detecting and appreciating the
distinctions upon which the arrangement is founded.

It is but little that can be known of the subject without forming a
collection of greater or less extent; for, as it would be uninstructive
merely to delight the eye with the bright colours and elegant form of
shells, without possessing correct information respecting them, so it would
be insipid and useless to learn technicalities without being acquainted by
personal observation with the subjects to which they are applied. The first
endeavour should, therefore, be to obtain a few shells as examples of the
larger divisions, and, when these are understood, to proceed with the
smaller groups, until a collection be formed to represent as many generic
forms as possible. It may be as well here to advise those who are forming a
collection to be very particular in every practicable instance to have the
shells properly named at the time of purchasing; as it will save much
trouble, and materially assist in the attainment of the desired object. To
this end, recourse should be had to those naturalist tradesmen, who unite
the attainment and diffusion of real scientific knowledge with their
commercial pursuits.

Supposing, however, that the person who desires to learn the science,
possesses a small parcel of unarranged and unnamed shells, without any
previous acquaintance with the subject, the following introductory
explanations, are drawn up with the view of enabling him, without further
assistance, to obtain a general insight into its principles, equal to that
of those who have studied it long and laboriously. To effect this, he must
read them, carefully comparing the descriptions with the figures referred
to, and with the specimens which he may have at command.

After describing the nature of the science and defining its objects, we
shall proceed to explain the structure of those objects, and the manner of
their growth. We shall then enter somewhat minutely into the principles of
classification, the distinctions upon which they are founded, and some of
the technical terms used to express them. After which we shall pass through
the arrangement of Lamarck, defining the general divisions adopted under
the terms of "_Classes_, _Orders_, and _Families_," as far as they are
capable of definition. The subdivision of the latter into _genera_ will
only be entered into so far as to enumerate the principal of them, the more
minute descriptions being reserved for the alphabetical part of the work.

Let none be discouraged by the number of generic distinctions proposed and
adopted in modern times; for if well defined, they will be found to
facilitate rather than encumber the science. The knowledge of species must
be the foundation of every system, and the greater their number, the more
necessary it becomes to subdivide them; if, for instance, all the species
now known were to have been included in the 50 genera of Linnæus, a single
genus would have contained many hundreds of incongruous species, in which
case it would be much more difficult to remember them, than if they were to
be divided into a far greater number of genera. Every well marked division,
however arbitrary its limits, tends to simplify the subject, and to
facilitate the researches of the student.

NATURE OF THE SCIENCE.

Conchology is the study of shells, viewed and described as to what they are
either in themselves, or in relation to the soft, inarticulate animals
which produce them, and of which they form a part. These animals are called
MOLLUSCA, and perhaps the best general description of them will be found in
De Blainville's "Manuel de Malacologie et de Conchyliologie." The following
is a translation, "Animal in pairs, the body and its appendages soft,
inarticulate (not jointed), enveloped in a muscular skin, commonly called
the mantle, which is extremely variable in form, and has developed either
within or upon it a calcareous portion, consisting of one or several
pieces, commonly called a SHELL."

The term Mollusca was formerly restricted to those soft animals which were
destitute of shells, although possessing in other particulars, the
characters described above, and it was used in order to distinguish them
from the TESTACEA, which were covered or internally supported by calcareous
parts. In the system of Linnæus, the soft portions are first arranged under
the general designation of "Vermes Mollusca," and described without regard
to the presence, absence, or character of the shells; and then the shells
are separately characterized under the appellation of "Vermes Testacea,"
without any further notice of the animal, than an indication of the genus
to which it belongs; thus the animal of Cypræa is said to be a Limax, and
that of Tellina a Tethys.

The nearest approach to correctness, and the most philosophical method of
study will be found in the modern system, adopted by Lamarck and his
followers, of observing these animals as a whole, and arranging them
according to the assemblage of characters which they present; of course
taking into consideration the existence or non-existence, form and
structure of the shell, on the same principle, which, in arranging the
vertebrated animals would lead us to study the hair, hoof, nails, claws,
&c. as well as the other parts.

At the same time, it must be admitted that there are many private
collectors of Shells who would find it a difficult, if not impossible task
to study minutely and successfully the soft parts of the Mollusca. Ladies,
for instance, could not be expected to handle with pleasure and
perseverance, these fleshy substances, which in order to be preserved from
putrefaction, must be kept in spirits; and yet such persons may, with
improvement and advantage to their own minds, enjoy the interesting and
scientific amusement of studying and arranging the clean and beautiful
natural objects which are so easily preserved, and so exquisitely curious
in their structure. Let it also be remembered, that if shells had not been
rendered commercially valuable, by the zeal and emulation manifested by
_mere_ Conchologists for the possession of rare specimens, few travelling
merchants and sea captains would have thought them worthy of a corner in
their cabins. In this case, few specimens being brought to the country, the
more Philosophical Naturalist would have been left without the means of
obtaining materials to work upon, or of attracting public attention to his
favourite pursuit.

On account of these and other considerations, it has been thought advisable
that the present undertaking should bear a purely conchological character.
The peculiarities of the shells alone being detailed for the assistance of
those who collect and study them, while at the same time, in deciding upon
their affinities and places, in the arrangement, it will be necessary to
take advantage of the conclusion to which those have arrived, who have
studied the animal in all its parts. And the conviction must be expressed,
that if ever a complete Natural System shall be formed it will result from
the labours of the last mentioned class of naturalists.

DEFINITION OF A SHELL.

Before entering minutely into the description of shells, it will be
necessary to distinguish from the true testaceous Mollusca two kinds of
animals which have formerly been associated with them. Of these, the first
is the class of CRUSTACEA, consisting of crabs, crayfish, &c. These differ
from shell-fish, not only in structure and chemical composition, but also
in the fact that the animal has jointed limbs, and that the substance of
the flesh is inseparable from the hard external covering, which invests
each particular joint as with a sheath; whereas the Molluscous animal is
but partially attached to its shell, from which it possesses the power of
partly withdrawing and returning. The second class is that to which the
sea-urchin, or Echinus, belongs, of which there are many genera and
species. The testaceous covering of Echini is composed of a number of small
pieces, placed edge to edge, forming a more or less globular external
covering to the flesh, which is supported in the centre by a number of
bones leaning upon each other in a pyramidal form. The _test_ is of a
fibrous texture, guarded on the outside with moveable spines, which turn on
ball and socket joints.

A true shell is composed of one or more calcareous pieces, commonly called
valves, each piece formed by a series of layers, applied obliquely upon
each other, in such a manner that each new layer begins within, and
terminates a little in advance of the one before it.

STRUCTURE AND GROWTH.

We shall now endeavour to describe the manner in which the growth of each
separate valve, or each regularly formed shell, proceeds from the nucleus.

Before the young animal has left the egg, if it be an _oviparous_ species,
or the body of the parent if _viviparous_, the nucleus of the shell is
generally formed, and specimens are sometimes preserved in which the young
shell is seen within the egg, as in the cut, fig. 1, 2; or adhering to the
inner surface of the full-grown shell by the dried mucus of the animal, as
seen in fig. 3.

[Illustration: 1. Egg of a Bulinus. 2. The same broken, shewing the young
shell. 3. The young of a Paludina, as seen in the aperture of the shell.]

In both cases, the nucleus is generally of a more horny and transparent
composition than the parts subsequently produced. As soon as the animal is
hatched, or, in other words, leaves the egg or body of the parent, of
course it begins to increase in size, and to require a corresponding
enlargement in the shell. To effect this, a small quantity of mucus
substance, secreted by the mantle of the animal, is deposited on the edge
of the aperture. When this is dry and become sufficiently hard, it is lined
by a more calcareous secretion; and these together form a new layer, which
is followed by others in succession; each new layer being larger than the
one that preceded it until the whole being complete, the full-grown animal
is invested with a shell commensurate with its own proportions. Thus from
the apex or nucleus the formation proceeds, as it were, downwards, taking
the shape of the part which secretes it, on which it is in a manner
moulded.

The nucleus, or first formed portion, may for technical purposes be
considered, mathematically, as the apex of a spiral cone. And here it must
be observed, that whether the shell consist of one or several pieces, each
piece has a separate nucleus, and the process of formation is separately
repeated with each. The word cone is used for convenience, and its meaning
extended so as to include all those structures which commencing at a point
enlarge downwards.

[Illustration: 4. Imaginary cone. _a._ Apex. _b._ Base. _l._ Lines of
growth.]

From the apex, the next layer is deposited on its edge, and advancing
beyond it necessarily adds to its extent. Thus, suppose for the sake of
illustration, the part marked _a_ in the diagram, fig. 4, to represent a
nucleus, the cross lines (_l_) will shew the consecutive layers, which
enlarge their circle as they add to their numbers. This disposition of
shelly matter into layers is marked externally by concentric striæ, or
_lines of growth_, while on the inside the edges of the laminæ are
consolidated into a kind of enamel. If a perpendicular section of a solid
portion of a shell were magnified, it would present, in many instances, an
appearance resembling the diagram, fig. 5; _a_ may be taken to represent
the horny part of the layers which form the outer coating, named
"_Periostaca_," or "_Epidermis_;" the undulating line _b_, is formed by the
edges of the calcareous layers, and causes the striæ, or lines of growth,
which are often distinguishable on the surface of the shell; the space _c_
is the middle part of those layers, and at _d_ they are consolidated into
the enamel which lines the interior.

[Illustration: 5. Supposed section of a part of a solid shell.]

In some species the layers are irregularly grouped together, and their
edges overlap each other, so that they are easily separable, and advancing
beyond each other, give a leafy appearance to the external surface. This
structure is termed _foliaceous_. A very familiar instance of this may be
observed in the common oyster. If a specimen of this shell be broken, the
substance will be seen to exhibit a degree of looseness, and a magnifying
glass will enable the student to trace distinctly the laminæ of which it is
composed. The accompanying representation of a magnified section (fig. 6)
will shew at _a_, the external surface, with the foliations or leaves; at
_b_, the parcels of layers which form them; and at _c_, the pearly
structure produced by their consolidation, and by the subsequently
deposited enamel which covers their external surface.

[Illustration: 6. Section of an oyster shell enlarged.]

CLASSIFICATION.

The classification of shells, that is, their systematic arrangement into
_classes_, _orders_, _families_, _genera_ and _species_, cannot be made to
depend entirely upon the characters observable in them, viewed by
themselves; for this reason, that many similarly formed shells form the
habitations of animals perfectly distinct, and that many molluscous animals
are found to agree with each other in every respect but in the form of
their testaceous support. There are, however, many important distinctions
to be observed in the shells themselves, leading to the establishment of
many of those very divisions, which would afterwards be confirmed by an
examination of the soft parts. It is necessary to attend, as far as means
and opportunity will allow, to _all_ the points of difference, both in the
shell and in the animal, in order to form, and in some instances even to
appreciate, a generic or larger distinction. It will therefore be our
endeavour to explain the general principles upon which those distinctions
are formed, and the manner in which they are applied and expressed in
detail by scientific writers.

NUMBER OF PIECES, OR INDEPENDENTLY FORMED PARTS.

The first, most simple and obvious division of shells, is that which
results from the number of separate pieces composing them. Hence the
distinction implied by the terms UNIVALVE, or consisting of a single piece;
BIVALVE, or composed of two pieces; and MULTIVALVE, or composed of more
than two. For an example of _univalve_, take a common whelk; for a
_bivalve_, take a muscle or a scallop; and for a _multivalve_, the
barnacle, or balanus, found adhering to the common oyster.

But although this arrangement may appear at first sight perfectly easy and
plain, some explanation will be necessary in order to guard the student
against understanding the above expressions in their strictest sense,
without qualification. Thus the univalves are said to consist of a single
piece, or spiral cone; but it would be more correct to speak of this piece
as forming either the whole or the principal part of the shell: for there
is in many instances, a much smaller flattened piece attached to the foot
of the animal, which being drawn in when it retires, closes the aperture as
with a kind of door, to which in fact the word valve might be very properly
applied; it is called however the OPERCULUM, and the little horny plate,
frequently drawn out by means of a pin from the aperture of a periwinkle,
will present a familiar example.

[Illustration: Accessary valves of a Pholas.]

The same may be said respecting the bivalves; for besides the principal
portions or valves of which the shell is composed, there are in many
species, one or two smaller separate portions, named "_accessary plates_"
by some authors. They are fixed by means of cartilages, on the back of the
hinge.--The engraving, fig. 7, represents the accessary valves of a species
of Pholas, which was on this account arranged by Linnæus with the
Multivalves. Nearly allied to the Pholades is a set of shells to which De
Blainville has given the name "_Tubicolæ_," or inhabitants of tubes. In
this case, the bivalve shell is connected with a testaceous tube or pipe,
to which it is attached either by one or by both valves, or in which it
lies attached only by the cartilages of the animal. In the genus
Aspergillum, the two small valves are soldered into the sides of the tube
in such a manner as to constitute a part of it. One of these shells, called
the Water-spout, might be taken up by a person not aware of its real
nature, and regarded as a pipe or tube prettily fringed, and nothing more;
but upon a closer examination, he would find the two valves, the points of
which are visible from the outside of the tube.

HABITS--_Land, Fresh-water, or Marine Shells._

Another distinction, leading to important results in classification, is
that which is derived from the nature of the element breathed by the
Mollusc. And although this consideration belongs more especially to the
study of the animal itself, yet the habits of the animal materially
influence the structure of the shell.

The TERRESTRIAL or LAND Molluscs live on land, breathe air, and feed on
plants and trees.--Those who find pleasure in horticultural pursuits will
at once call to mind a too familiar example of these Molluscs in the common
garden snail. The Land-shells are all univalves, and constitute a family in
the Lamarckian system under the name "_Colimacea_," or snails,
corresponding with the Linnean genus Helix.--They are generally light in
structure and simple in form.

The AQUATIC, or Fresh-water Molluscs, such as the Planorbis, commonly
called the Fresh-water Snail; the Unio--known by the name of Fresh-water
Muscle, is found in ponds, ditches and rivers. The _epidermis_ of these is
generally of a thick, close-grained character, and they are subject to
corrosion near the umbones. There are but few genera of fresh-water shells
besides the Uniones, among bivalves, and the "Melaniana" among univalves.
Concerning the former it may be observed, that they are all pearly within,
and the colour of the thick horny coating embraces all the varieties of
brownish and yellowish green.

The MARINE, or _sea-shells_, belong to all the classes and orders, and
include by far the greater number of species. They vary in the habits of
the animal, and consequently in the situations in which they are found.
Some are found buried in sand and marine mud, and are named "_Arenicolæ_"
or inhabitants of sand; others in holes of rocks and other hard substances,
then they are named "_Petricolæ_,"--some of these latter form the holes in
which they live by corroding or eating away the stone. A section of these
form the family of "_Lithophagidæ_," or stone-eaters, of Lamarck. Others,
again, take up their parasitical abode in the bodies of animals, and feed
upon their substance; as for instance, the Stylifer, which is found in the
vital part of star-fish, and Coronula, and Tubicinella, found buried in the
skin of the whale.

LOCOMOTION--_Attached, Unattached._

A much more subordinate source of distinction arises from the freedom or
attachment of the shells. Some of them float or walk freely in their
natural element; others are fixed or attached to foreign bodies. Among
those which are attached, there is again a difference as to the mode of
attachment. Some are united to foreign bodies by means of a glutinating
substance, secreted by the animal, and joining part of the surface of the
shell to that of the stone, coral, or other substance. In this way shells
are fixed to each other in groups; this is the case with the Spondyli among
bivalves, and the Serpulæ among univalves. M. de Blainville applies the
term "_Fixæ_" to these shells. Others are kept in a particular place by
means of a _Byssus_ or Tendinous fibrous line or bunch of silky hairs,
acting as a cable, and allowing the Mollusc to ride as it were at anchor.
This Tendon is connected with some part of the animal from which it passes
through an opening or hiatus in the shell, as in the Terebratula and the
Mytilus.

[Illustration]

In the former, represented by the cut, fig. 8, the tendon passes through a
perforation in the upper valve; and in the latter, Mytilus, fig. 9, the
byssus passes out between the valves.

Before proceeding to explain the characters of the different groups,
according to the modern system of classification, it may be desirable to
explain the terms by which the different parts and characters are
described, and to shew the manner in which the shells are measured. For
this purpose we shall treat of the general divisions separately. We begin
with

UNIVALVE SHELLS.

In considering Univalves merely with reference to their mathematical
construction, the first point demanding our attention is, whether they are
symmetrical or non-symmetrical, or, in other words, whether a straight line
drawn through the shell would divide it into two equal parts. The greater
part of univalves are non-symmetrical, being rolled obliquely on the axis;
but many are symmetrical, being rolled horizontally on the axis. The
Nautilus presents an illustration of the latter; the Snail is a familiar
example of the former.

_Symmetrical Univalves._

[Illustration]

In describing these it will be well to commence with the most simple form,
such as the Patella,--taking a conical species as an example. In this it
will be observed that there is no winding or curvature, but a simple
depressed cone, and that the line _a_, _p_, divides it into two equal
parts.

The _anterior_, _a_, (_cut_, fig. 10) is known by the interruption of the
muscular impression which surrounds the central disc (_d._) This
interruption of the muscular impression is in the place where the head of
the animal lies in the shell. The impression itself is caused by the
fibrous muscle which attaches the animal to the shell. The apex (_a_) in
Patella, generally leans towards the anterior (_a_) part of the shell, and
away from the posterior (_p_); and this circumstance has caused some
mistakes, because in Emarginula the apex leans towards the posterior; and
students, instead of examining the muscular impression, which is the only
criterion, have only noticed the direction in which the apex turned, and
concluded that to be the anterior, towards which it inclined. The lines or
ribs running from the base to the apex of the shell, in the direction _r_,
are called _radiating_ lines; and those which encircle the cone in the
direction _c c_, from front to back, are very properly described as
_concentric_. The _length_ is measured from front to back in the line _e_;
the breadth, from side to side, in the line _b_; and the depth from the
apex to the base.

Let it be observed that patelliform, or limpet-shaped shells are not all
symmetrical; Umbrella, Siphonaria, Ancylus, &c. will form exceptions, of
which we have yet to speak. And the learner may also be reminded that the
Limpets themselves are not _all_ regular in their form: for as they adhere
to rocks and other rough surfaces, and are so little locomotive, in many
instances they partake of the inequalities of the surface, and conform to
its irregularities. This adherence is not effected by any agglutinating
power in the animal, nor by any tendinous process like that described
above; but simply by means of the foot of the animal acting as a sucker.

The next variation in symmetrical univalves is to be observed in the
tubular, curved form, the example of which will be the Dentalium, fig. 12.

[Illustration: Dentalium Elephantinum.]

This has an opening at the anterior termination _a_, called the aperture.
The opening at the posterior end (_p_) is named a fissure, or perforation.
The ribs running along the sides of the shell are _longitudinal_, or
radiating. And the lines round the circumference are _lines of growth_, or
_concentric_--each one having in succession, at earlier stages of growth,
formed the aperture. They are described as concentric, or transverse.

_Symmetrical Convolute Univalves._

The Nautilus, the Spirula, the Scaphite, and the Ammonite are the leading
types of this form; but when we use the term symmetrical, in reference to
these, the word must not be understood in its strictest sense, for no shell
is _perfectly_ symmetrical: but it means that there is no perceptible
difference in the proportion of the two sides; as in the human body, the
right side is larger and more powerful than the left, yet to a degree so
small that it gives no apparent bias to the figure.

CHAMBERED SHELLS.

Many of the shells now under consideration are chambered, that is, the
internal cavity is divided into separate compartments by plates reaching
across it, named _Septa_; and the only connection between the chambers is
formed by the small pipes passing through them, to which the name of Siphon
is attached.

_Septa._

The septa are _simple_ in some species, as in the Nautilus, fig. 13. In
others they are _undulated_, having waved edges, as in some species of
Ammonites; in others they are _angulated_, as in Goniatites, fig. 480 in
the plates; and in the greater number of instances, among the Ammonites,
they are _arborescent_, or branched.

[Illustration: 13. Section of Nautilus.--14. Undulating Septa.--15.
Arborescent Septa.]

In the above section of a Nautilus, fig. 13, diminished in size, showing
the whorls and chambers (_c_), it will be seen that the edges of the septa
(_s_) are formed in one simple curve. In fig. 14, the upper part of an
Ammonite, the undulating line will be seen; and in fig. 15 a specimen is
given of the arborescent septa.

_Siphon._

The Siphon is _dorsal_ when placed near the outside of the whorls;
_central_ when near the middle; and _ventral_ when near the inside of the
whorl, or that part which leans against the last volution. When it passes
uninterruptedly from one chamber to another, it is described as
_continuous_, as in the case of Spirula; when, on the other hand, it only
passes through the septum a little distance, and opens into the chamber, as
in Nautilus, it is _discontinuous_.

_Whorls of Symmetrical Univalves._

They are _disunited_ when they do not touch each other, as in the case of
Spirula (fig. 471 in the plates); but in the contrary case they are said to
be _contiguous_. In some species of Nautilus the whorls overwrap each other
in such a manner that the early whorls are entirely covered by the last,
the edges of which reach to the centre of the disk: the spire is then said
to be _hidden_; as in the Nautilus Pompilius. In Nautilus umbilicatus the
spire is nearly hidden, the whorls not quite covering each other; but in
the greater number of the Ammonites, the largest part of the preceding
whorls is seen. To express the degree in which the whorls overwrap each
other, has caused much difficulty in concise descriptions. Perhaps it would
be well to apply the term _spiral disc_ to so much of the shell as is seen
besides the last whorl, and to describe it as large or small in diameter,
compared with the whole: or to say that the whorls of the spire are half,
or one-third, or one-fourth covered, as the case may be.

_Aperture of Symmetrical Univalves._

In Ammonites Blagdeni and some others the aperture is of an oblong square;
it is then said to be _sub-quadrated_; in Nautilus triangularis it is
_angulated_; in Ammonites Greenoughi it is of an interrupted oval shape,
described as _elliptical_. In the greater number of Orthocerata, it is
rounded or _circular_. The entrance of the last whorl into the aperture of
some rounded species of Nautilus causes it to take a _semi-lunar_ form; if
rounded at the sides it is said to be reniform or kidney-shaped; if pointed
at the sides it is _semi-lunar_; and in some species of Ammonites, it is
five-sided or _quinque-lateral_.

_Measurement of Symmetrical Conical Univalves._

[Illustration]

The _width_ is measured across the aperture, which is the widest part of
the shell. The _length_ (_l_) from the dorsal part (_d_) of the aperture to
the dorsal part of the _whorl_ (_d_) on the opposite part of the shell. The
_ventral_ part of the whorls is that nearest to the axis, and the _dorsal_
that which forms the outline of the figure.

NON-SYMMETRICAL UNIVALVES.

These are _conical_, _irregular_, _spiral_, or _convolute_. The _conical_
form is when there is no enrolment of the apex. Although the Patellæ were
described as symmetrical, there are several species of Patelliform shells
which are not symmetrical. In Umbrella, for instance, the apex is oblique,
the shells being placed obliquely on the animal. In the genus _Siphonaria_,
there is a groove on one side, where the brachia or gills of the animal
rest. In the genus Ancylus, it will be observed that the apex bends on one
side, and the animal is like the Limnæa, which has a spiral shell. The cup
and saucer Limpets, or Calyptrædæ, present a group which requires to be
described, differently from the symmetrical or true Limpets. Their
structure is very curious, and they vary considerably among themselves,
some of them being simply conical, others nearly flat, or discoidal, and
others more or less spiral. But their principal peculiarity consists in
their having a small internal process or plate variously shaped, commonly
named their _septum_.

_Septa of Limpets._

The septa of Limpets assume a variety of forms, the principal of which will
be seen in the accompanying engravings.

[Illustration]

The form from which the group derives its generic appellation is that of
the cup-shaped or _Cyathiform_ species (fig. 17). In the Crepidulæ, or
Slipper-Limpets, the septum is flat, reaching across the opening, like the
deck of a vessel; it is then described as _transverse_ (fig. 20). In
Calyptræa Equestris, it has two prominent points, and is described as
_bi-furcated_ (fig. 18). In another species, it is a three-sided plate
rather spiral at the apex (fig. 19).

_Measurement of Cup and Saucer Limpets._

[Illustration]

The line marked _a_, _p_, _ll_ indicates the direction in which the shell
is to be measured for _length_. _a_ indicates the _anterior_, _p_ the
_posterior_. The line _d_ (fig. 23), from the apex to the base, is the
_depth_. The line _b_ (fig. 28), is in the direction of the breadth.

_Irregular non-symmetrical Univalves._

Serpuliform shells are irregularly twisted (_tortuous_) hollow tubes, which
were formerly considered to have been secreted by a kind of worm, but now
known to be the shells of true Molluscs, of a kind not very widely
differing from those which have regularly spiral shells. The greater part
of these are attached to foreign bodies, or to each other in groups. Some
are attached by the whole length of the shell, they are then said to be
_decumbent_. Some of these are coiled round like the Spirorbis, the little
white shell seen on the carapace of the Lobster or on leaves of sea-weeds;
they are then said to be discoidal; others again, such as the _Vermetus_,
approach more nearly to the spiral form. The deviation from the regular
spire only taking place after the few first volutions.

SPIRAL NON-SYMMETRICAL UNIVALVES.

As these constitute the largest class, it will be necessary to dwell upon
them in detail. First as to _measurement_.

[Illustration]

The length is measured from the apex, to that part of the aperture _a_
(fig. 24), at the greatest distance from it. The _breadth_ is in the
opposite direction. The _anterior_, or front part of the aperture, is
marked _a_, where the head of the animal protrudes.

_Spire of non-symmetrical Univalves._

[Illustration: Fig. 25, _obtuse_; 26, _acute_; 27, 28, _decollated_; 29,
_concave_; 30, _papillary_; 31, _mammellated_; 32, _discoidal_.]

In counting the whorls of which the spire consists, we commence at the
apex, and reckon downwards to the last, or body whorl. The spire is
described as being long or short in relation to the aperture: in which
case, all that is above the aperture is measured with the spire. Its apex
requires particular notice, as the character of the whole shell frequently
depends upon the particulars observable in this part. It is sometimes
_obtuse_, or blunt; sometimes _acute_, or sharp. In the Cones it is
frequently flat, and in Planorbis it is concave. It is sometimes of a
different structure from the rest of the shell, retaining the horny and
transparent appearance which characterized it when the animal was first
hatched. The Tritons present an instance of this, although it is not always
observable, owing to the tenderness of the substances which causes it to
break or fall away in many specimens. A very remarkable instance also
occurs in Bulinus decollatus (cut, fig. 27, 28), so named, because the
apex, to the depth of several whorls, falls off, and the shell is
_decollated_. In this, and many more instances, among Pupæform land shells,
the occurrence of this circumstance seems to be by no means rare or
accidental, a provision having been made for filling up the opening by a
septum. A _papillary apex_ is one which is swelled at the extremity into a
little rounded nob, or nipple; and a _mammellated_ apex is one which is
rounded out more fully into the shape of a teat.

_Whorls._

The spire is described as consisting of _numerous_ or _few_ whorls, and
sometimes the number of them is particularly stated. A whorl consists of
one turn of the spiral cone. The whorls are described as _flattened_, when
the sides are not bulged out so as to cause the outline of the spire to
deviate considerably from straightness: when the contrary is the case, the
whorls are said to be _ventricose_, and either _rounded_ or _angulated_.
The degree of rapidity with which the whorls become enlarged presents an
important source of distinction. The _suture_, or seam, which separates one
whorl from another is also noticed as being _distinct_ or otherwise;
_canaliculated_, or grooved; or covered by an enamel, which in some
instances is swelled into a ridge or _tumid_.

[Illustration: Fig. 33, _few_; 34, _numerous_; 35, _rounded_, _ventricose_;
36, _angular_, _ventricose_; 37, _flattened_.]

_Suture._

[Illustration: Fig. 38, _canaliculated_; 39, _enamelled_.]

_Varices._

Varices are caused by periodical rests or stoppages in the growth of the
shell, when the edge of the aperture thickens, and renders the shell as
complete as when full grown. Again, after an interval, another check takes
place, and another thickened edge is formed, and so on in succession, until
the animal arrives at maturity, and the shell is full-grown. The thickened
edges successively forming the aperture, remain visible on the outside,
through all the subsequent stages. When these rests take place at frequent
periods, the varices will of course be numerous as in Harpa and Scalaria.
They occur at regular or irregular distances, varying in shape and other
characters. When the varices occur at regular intervals, and form a
connected ridge from whorl to whorl up the spire, they are said to be
_continuous_, as in Ranella; when on the contrary, the varix on one whorl
does not come in contact with that on the other, they are described as
_discontinuous_. In order to distinguish a regular varix from a mere
external ridge, it will be sufficient to notice whether its edge overlaps
the external surface, and whether it resembles the open edge of the
aperture, which true varices do.

[Illustration: Fig. 40, _numerous_; 41, _few, continuous_; 42, _few,
discontinuous_.]

_Aperture._

The aperture or opening of the spiral tube, was formerly described as the
mouth; a term calculated to convey an erroneous impression, when applied to
a part of the shell which has no correspondence with the mouth of the
animal. The word _aperture_ is used by modern writers in a general sense,
including the cavity, its edge, and the canals. The cavity itself is
distinguished in various shells as to its shape, which depends much upon
the degree of modification produced by the last whorl. In some cases, as in
Cyclostoma, where the aperture stands apart from the last whorl, the shape
is round, or nearly so. The Scalaria presents a good example of this. In
others, where the inner edge or lip, wrapping over the body whorl is nearly
straight, the aperture is _semi-lunar_, or half-moon shaped: this is
remarkable in the "_Neritacea_" of Lamarck, named, on that account,
"_hemi-cyclostomata_" by De Blainville. In a great number of instances, the
lower part of the body whorl enters obliquely into the upper part of the
aperture, the result being a _pyriform_, or pear-shaped opening. The
aperture is described as _long_ when it is largest in the direction of the
axis, and _wide_, in the contrary case. The _anterior_ is the part at the
greatest distance from the apex, and the body whorl; the _posterior_, the
part nearest to the apex. Thus some apertures are described as _posteriorly
contracted_ and _anteriorly widened_, or the reverse. A _linear_ aperture
is one contracted in its whole length, as in Cypræa. When the whorls are
angulated, a _trigonal_ aperture is the result, as in many species of
Trochus. Some are _transversely oval_, that is in an opposite direction to
the axis, and others _longitudinally oval_. When the whorls are formed with
two outer angles, a somewhat quadrated aperture is formed. There are other
variations too numerous to mention.

_Apertures._

[Illustration: Fig. 43, Helicina, _semilunar_; 44, Pirena, _pyriform_; 45,
Cypræa, _linear_; 46, Trochus, _trigonal_; 47, Cyclostoma, _rounded_; 48,
Chilina, _posteriorly contracted_; 49, Stomatia, _transversely oval_; 50,
Murex, _longitudinally oval_.]

The entire edge of the aperture described generally, is named the
Peritrême, but this term can only be conveniently applied in cases where,
in some at least of its characters, it is the same all round, so that one
descriptive term is applicable to the whole. As, however, this is of rare
occurrence, it is found convenient in descriptions to separate the rim from
the outer lip. In a great number of instances, this is done naturally, by a
canal, or notch at the anterior or lower extremity, and by the posterior
union of that part which overlays the body whorl with the other portion. At
these two points the outer and inner lips separate from each other: we
therefore describe the

_Canals of the Aperture._

When there is neither notch nor canal, anteriorly or posteriorly,
interrupting the edge of the aperture, it is described as entire. When
there is a notch or sinus at the anterior extremity, it is said to be
_emarginated_. When the edge of this notch is expanded, and drawn out in
the form of a beak, it is said to be _canaliferous_, or to have a _canal_.
When, in addition to this, the lips are thickened and contracted
posteriorly near their junction, and drawn out so as to form a groove, it
is said to be _bi-canaliculated_, or to have two canals. The _anterior
canal_ is said to be long or short, according to the proportion which it
may bear to the rest of the shell. Thus the canal of Ranella ranina (fig.
393 in the plates), may be described as _short_; while that of Murex
haustellum, (fig. 396, pl.) is _long_. When it is wide near the aperture,
and becomes gradually contracted towards its termination, it is said to be
_tapering_, as in Pyrula (fig. 388, pl.); when the termination is sudden,
it is described as _truncated_. If, on placing the shell upon a plane, with
the aperture downwards, the canal is seen to rise upwards, it is
_recurved_. In Buccinum and Nassa it is turned suddenly over the back, and
forms a short, curved elevation; it is then described as _recurved_ and
_varicose_. If the edges meet, so as to form a tube, it is said to be
closed, as in some species of Murex and Typhis. The posterior canal is, in
some cases, _free_, or standing out from the spire, as in some species of
Ranellæ; while in others it is _decumbent_, running up the sides of the
spire, as in Rostellaria (fig. 402, pl.).

_Canals._

[Illustration: Fig. 51, Fasciolaria, _truncated_; 52, Nassa, _recurved_,
_varicose_; 53, Cerithium, _recurved_; 54, Typhis, _closed_.]

_Lips, or edges of the Aperture._

The part of the edge of the aperture next to the body whorl is named the
_inner_, or _columellar_ lip. Posteriorly it commences at the point of
union with the outer lip, where that touches the body whorl, the junction
being generally marked by an angle, and sometimes by a canal. Anteriorly it
terminates where there is generally seen a notch or canal, or sudden angle,
from which the outer lip proceeds. The part which setting out from the body
whorl, and proceeds outwards at a distance from the axis, till it reaches
the anterior canal or notch (or its place in case of absence) is named the
_outer lip_. In many cases the edges are united in such a manner, that it
is difficult to distinguish where the inner lip terminates, and the outer
lip commences: when this is the case, it is usual to describe the margin or
peritrême, as a whole, without distinguishing the parts. The _outer_ lip,
sometimes called the right lip, or _labrum_ of continental writers, is
sometimes acute, not being of thicker substance than the remainder of the
shell. In other cases it is _obtuse_, or thickened and rounded at the edge.
When thickened and turned backwards it is described as _reflected_; when,
on the other hand, it is turned inwards towards the axis, as in the
Cyprædæ, it is _inflected_, or involute. When it is _toothed_, a
distinction must be observed as to whether the dentations are external or
internal. If the teeth are small and numerous, it is _denticulated_; if
larger, it is _dentated_; when expanded into a kind of wing, as in some
species of Strombus and Rostellaria, it is described as _alated_; and a
family in Lamarck's system is named "Alatæ," from this very circumstance.
In some of those which are expanded, the expansion is divided into
separate, attenuated portions, they are then said to be digitated.

_Outer Lips._

[Illustration: Fig. 55, Helix, _reflected_; 56, Cypræa, _involute_,
_denticulated_; 57, Sera, _alated_; 58, Murex, _digitated_; 59,
Rostellaria, _dentated_.]

The _inner_ lip, sometimes named the _columellar_ lip, or "_labium_," is
subject to similar variations as to thickness, dentition, &c. That portion
of it which lies upon the body-whorl is frequently distinguished from that
which intervenes between it and the notch or canal. De Blainville,
restricting the term _lip_ "bord gauche" to the former portion, applies the
term "columella" to the latter; and in some instances this may be the more
convenient method of describing the part in question. The columellar lip is
sometimes _detached_ entirely from the body of the shell, as in Murex
haustellum; in others it is _decumbent_, or lying over the last whorl,
although quite distinct, and in some cases, _thickened_, _callous_, or
_tumid_.

At the lower or anterior part, sometimes called the _columella_, there are
in many instances flattened, laminated folds; these are particularly
conspicuous in the genera Cymba and Melo, where, being obliquely spiral and
laminar, they are extremely elegant, presenting to the eye graduated
repetitions of the line of beauty. In other cases, as in the Turbinellæ,
they are more horizontal and thickened.

In some cases the columella is swelled into a varicose mass; as in Oliva,
Ancillaria, &c.; it is then described as _tumid_ or varicose. It is
sometimes _tortuous_, and sometimes straight, and is susceptible of many
variations, too minute and particular to be described in this part of the
work.

COLUMELLAR LIPS.

[Illustration: Fig. 60, Melo, _obliquely plaited_; 61, Turbinellus,
_horizontally plaited_; 62, Ancillaria, _varicose_, _tortuous_; 63, Natica,
_straight_.]

OPERCULUM.

The aperture of many species of shells remains constantly open; but in a
great number of species it is occasionally closed, whenever the animal is
retracted within the shell, by a calcareous or horny piece called the
operculum. This must be distinguished in the first instance from another
kind of calcareous covering, which in some univalve shells serves to close
the aperture during a certain portion of the year. This piece, named the
_epiphragm_, although hardened and shelly in appearance, is no real part of
the animal or of the shell; being only a secretion temporarily hardened,
for the purpose of defending the animal from external influences during the
_hibernating_ or _torpid_ season, to be dissolved when that season is at an
end. On examining this piece, it will be observed that it is not formed in
regular layers like the rest of the shell; while the true operculum is of a
regularly laminated structure, having a nucleus and receiving obliquely
deposited additions, either in a lateral spiral or concentric direction. It
is attached to the posterior part of the foot on the upper surface; and
when the animal retires within its shell, that part of the foot enters
last, drawing the operculum after it, and thus closing the aperture.

The opercula of various shells differ in the first place as to their
chemical composition. They are _calcareous_ when formed principally of
calcareous matter, like the rest of the shell, as in Neritina, Nerita, and
some others. They are _corneo-calcareous_, when upon an internal lamina of
horny consistency there is a thickened layer of shelly matter. This is the
case with shells of the genus Turbo and Phasianella, which are on this
account distinguished from those of the genus Trochus; the opercula of the
latter being horny or _corneus_.

The size of the operculum is distinguished by comparison with the rest of
the shell; thus, those of Strombus, Cassis, &c. are small; while those of
Cyclostoma and others are large, filling up the cavity at its outer edge.

The direction in which the successive layers are deposited, forms another
ground of distinction. The disc is formed in some instances of a series of
whorls, the apex or nucleus being more or less central; if these whorls are
numerous, the operculum is described as _multispiral_, as in shells of the
genus Trochus; if few, as in Cyclostoma, it is _paucispiral_. In some
instances the flattened spire consists of but one whorl, it is then
_unispiral_; and when scarcely one turn is completed, it is described as
_subspiral_. When the layers are applied upon each other in such a manner
that the nucleus is central, and the edges of the subsequent layers are
extended beyond each other all around, so as to form rims, the operculum is
described as _concentric_; if the nucleus is lateral, or at one side
without being spiral, it is _lammellated_; and when it forms a terminal
point, enlarging in the form of a finger-nail or claw, it is
_unguiculated_. In the operculum of a Neritina, there is a lateral process,
by means of which it is locked into the columella, the term _articulated_
is then applied. In that of Navicella, there is also a process which
appears to radiate from the nucleus, it has therefore been described as a
_radiated_ operculum.

_Opercula of Spiral Univalves._

[Illustration: Fig. 64, _multispiral_; 65, _paucispiral_; 66, _concentric_;
67, _articulated_; 68, _radiated_; 69, _lammellated_; 70, _unguiculated_.]

BIVALVE SHELLS.

Bivalve shells, named Conchacea by Lamarck, are those which consist of two
principal portions united to and folded upon each other by means of a
hinge. The pieces united compose the shell, while each piece separately is
called a valve. Considering the bivalve shell as a whole, it will be
necessary, in the first instance, to describe the position in which it is
to be observed, in order to give the student a clearly defined notion of
what is intended, when terms expressive of height, depth, length, breadth,
&c. are used, as well as when the anterior and posterior extremities are
spoken of. For this purpose, we must suppose the animal to be living and
creeping along the bed of the sea by means of its foot; where this foot
protrudes, will be the _ventral margin_, and the opposite part the _dorsal
margin_ of the shell. There will then be a valve on each side; and if we
further suppose the animal to be walking forward with its back to the
observer, the _right_ and _left_ valves will correspond with his right and
left sides.

_Measurements._

[Illustration]

The _length_ will be measured from _anterior_ (_a_) to _posterior_ (_p_),
and the lines of growth running in the same direction will consequently be
_longitudinal_ or _concentric_; _transverse_ of some authors. The height
will be from the umbones (_u_), to the _ventral margin_, and lines or bands
in that direction are termed _radiating_; longitudinal, according to some
authors.

The points from which the growth of the shell commences, are called the
_umbones_; these usually turn towards the anterior part of the shell: if
this circumstance fails to point out the anterior, it may in many cases be
distinguished by the muscular impressions of the mantle. If this has a
sinus or winding, it is always near the posterior muscular impression; and
in all cases where there is an external ligament, it is on the posterior
side.

There is sometimes an impression near the front of the umbones, which forms
a semicircle on each valve; the space within this semicircle is called the
_lunule_ (wood-cut, fig. 71 and 72, _l. l. l._); a corresponding
depression, when it exists on the posterior margin near the umbones, is
named the escutcheon.

_Hinge._

[Illustration: Fig. 73, _l t_, lateral teeth; _c t_, cardinal teeth; _c_,
cartilage under the ligament; _l_, ligament; _f_, fulcrum of the ligament.]

The _hinge_ of the shell is on the _dorsal_ margin, and is composed of the
various apparatus by which the two valves act upon each other in opening
and shutting. It consists of a _ligament_, which is placed on the dorsal
margin, just at the back of the umbones, and unites the two valves
together; the _cartilage_ or thick gristly elastic substance, sometimes
found close to the _ligament_, to which it then forms an inner coating, and
sometimes received into a pit within the shell. It serves the purpose of
keeping the shell open when not forcibly closed by the adductor muscles. An
inner layer of shelly matter upon which are placed teeth, and pits to
receive them on the two valves reciprocally. Each of these it will be
necessary to treat of more at large; observing, at the same time, that in
some species of Bivalves these parts may be wholly or partially wanting.
Thus we meet with some shells, such as the Muscle, without teeth; and there
is the group containing Pholas, &c. the hinge of which is destitute of
teeth and ligament, the two valves being kept together by loose cartilages,
and by the contracted space in which they are confined.

_Ligament and Ligamentary Cartilage of the Hinge._

These two distinct substances have been described by many writers as
though, composing the same mass, they were of one substance; but the
difference may very easily be explained. The _true ligament_ is external,
being fixed on the edge of one valve behind the umbones, and passing over
in an arch to the corresponding edge of the other, very correctly retaining
the name of _ligament_, because it serves the purpose of binding the two
together. The thick, elastic substance, which Mr. Gray names the
_cartilage_, is sometimes found in connexion with the ligament, so as to
form one mass with it, although it is always separable and placed within
it: it is sometimes placed quite within the shell, and separated from the
ligament, in a pit or hollow formed for its reception in the hinge lamina,
near the centre. It is found in both valves, and being elastic, the portion
in one valve presses against that in the other, so as to keep the valves
apart, unless voluntarily closed by the adductor muscles of the animal. The
ligament is sometimes spread over an external area, as in Arca, while the
cartilage is placed in several grooves of the same area, beneath the outer
covering.

_Hinge lamina, Teeth and Fulcrum of the Ligament._

In a great variety of cases, there is a thickening of the substance of the
shell within, under the dorsal margin; this is named the hinge lamina. It
is sometimes merely callous; but in many cases it has raised _teeth_ in
both valves, those in one valve entering into corresponding cavities in the
other. Those which are placed immediately below the umbones, and seem to
take their rise from beneath them, are called _cardinal teeth_; those at a
distance from the umbones, which are seen to lie along the upper margin of
the shell are named _lateral teeth_.

When the cardinal teeth terminate in a double point, which is not
unfrequently the case, they are said to be _bifid_. The lateral teeth, in
various species, are distinguished as terminating _near_ to, or at a
_distance_ from the umbones. In the Nuculæ and Arcæ there is a row of teeth
placed across the hinge lamina. In which case, the lateral cannot be
distinguished from the cardinal teeth.

_Muscular Impression._

[Illustration: Fig. 74. _a, anterior; p, posterior; m i, muscular
impressions._]

Lamarck divides the Bivalve shells into two general orders; the first is
named "Dimyaria," having two adductor muscles; and the second,
"Monomyaria," having but one. These adductor muscles are used for the
purpose of drawing the valves together, being composed of contractile
fibrous gristle, fastened firmly to the inner surface of each valve. The
place where they are thus fixed may be seen when the animal is removed, by
depressed areas, which are generally pretty well defined, and are named
_muscular impressions_. Where there is but one adductor muscle, there will
be but one of these impressions near the centre of each valve, but in the
Dimyaria, where there are two, the impressions are seen, one on the
anterior, and one on the posterior of each valve, just below the _hinge_
lamina. They are sometimes _complex_, that is composed of several portions
in a group; but in general, they are simple and well defined.

They are also described as large or small, in proportion to the size of the
shell; regular or irregular in form. The animal is attached to the inner
surface by the fibrous portions of the mantle, which creates a linear
impression or _cicatrix_, commonly described as the _palleal impression_,
or muscular impression of the mantle. It runs near the ventral margin from
one muscular impression to the other, sometimes in a smooth _continuous_
line or band, and sometimes in an interrupted series of small impressions.
Near the point of union with the posterior muscular impression, there is
sometimes a more or less considerable winding inwards towards the centre of
the shell, and back again towards the point of union. This is named the
_sinus_, and is distinguished as being _angular_ or _rounded_, large or
small, according to the species. When it enters towards the centre of the
shell in a tongue-shaped outline it is said to be _ligulate_. Where it
exists it affords a certain index to the posterior side of the shell; as it
is the region through which the excretory tubes pass.

_Umbones._

These are the prominent points of the dorsal edge, where the growth of the
shell commenced, and are called beaks, by some English writers. In some
instances they are close to each other; in others they are rendered distant
from each other by the intervention of areas in the hinge, as in Spondyli,
&c. In Pectunculus they are _straight_; in Venus _curved_ towards the
anterior margin; in Isocardia, _spiral_; in Chama, _decumbent_; in Diceras,
_free_. In shells subject to external corrosion, the process commences at
the umbones.

[Illustration: Fig. 75, _distant_; 76, _straight_; 77, _curved_; 78,
_spiral_; 79, _decumbent_; 80, _free_; 81, _close_.]

GENERAL CHARACTER OF BIVALVES.

When the _breadth_ is spoken of, the distance between the most convex parts
of both valves, when closed, is intended; but when an expression implying
_thickness_ is used, it refers to the substance of each valve: it is
important to bear this in mind, as many persons have been misled by
descriptions in which the distinction has not been attended to. Glycimeris
(fig. 67 in the plates) is a _thick_ shell, but Anatina (fig. 69 in the
plates) is a _broad_ one.

_Regularity._

A great number of Bivalves are extremely regular in their form. These are
generally locomotive, and consequently free from those obstructions in
growth occurring to stationary shells, which being confined in a particular
position, or to a particular spot, modify their shape according to the
substance with which they come in contact, and thus become irregular. This
is generally the case with shells which are attached to submarine
substances, such as Spondyli, Oysters, &c.; and the degree of irregularity
will depend upon the extent of surface involved in the attachment. In the
case of fixed shells, the attached valve is usually termed the under valve,
and the other which moves freely upon the hinge, is termed the upper valve.

_Form and Proportions._

Bivalves are said to be _equivalve_ when the two valves correspond in
extent, breadth, and thickness; and of course _inequivalve_ in the contrary
case. They are _equilateral_ when a line drawn from the umbones to the
ventral margin would divide the shell into two nearly equal parts; and of
course _inequilateral_ in the opposite case, which occurs in the great
majority of instances.

A Bivalve is said to be _compressed_, when the distance is small from the
most prominent part of one valve to that of the other. It is _cylindrical_
when lengthened, and more or less rounded in its breadth, as in Lithodomus
(fig. 161 in the plates). It is _cordiform_ when the shape presents a
resemblance to an imaginary heart, as in Cardium cardissa (fig. 122 in the
plates), and in the Isocardia (fig. 126 in the plates). It is _linguiform_
when it resembles a tongue in shape, as in Vulsella (fig. 185 in the
plates); _rostrated_ when it protrudes at either extremity, and terminates
in a kind of point, as in Sanguinolaria Diphos (fig. 99 in the plates);
_truncated_ when it ends in a square or angle, as if cut off; an example of
which may be seen in Solen (fig. 60 in the plates).

Other Bivalves are distinguished as being _auriculated_, having processes
flattened and expanded on either side of the umbones, as in Pecten (cut,
fig. 82). When there is one of these on each side of the umbones, it is
_bi-auriculated_; when only on one side, it is _uni-auriculated_. When the
expansion is very broad, as in Unio alatus (fig. 142 in the plates), and in
the Hammer Oyster (cut, fig. 83), the term _alated_ is used.

[Illustration: Fig. 82, _auriculated_; 83, _auriculated_, _alated_.]

With regard to these alated species of _Uniones_, it is necessary to
observe that they are also "_adnate_," as it is termed; the two valves
being joined to each other by the dorsal edge of the expanded parts, and
united so completely in substance with each other, that they cannot be
separated without being broken. Many other terms are used to express
difference in Bivalves, but being generally applicable to Univalves and
Multivalves, as well as to them, they will be found explained at large in
the alphabetical part of the work.

MULTIVALVE SHELLS.

These are of three different kinds; first, the "_dorsal_," as they are
termed by Linnæus, because they form a ridge in the back of the animal.
They are composed of eight pieces, or separate valves, placed in a
longitudinal series, being joined to each other by inserted lamina, and
named _Articulata_ by De Blainville, on that account. The genus Chiton is
the only example of this kind of Multivalves.

[Illustration: Fig. 84, 85, Chiton. _a_, anterior; _p_, posterior; _d_,
dorsal ridge; _l l_, lateral areas of the valves; _c c_, central areas; _i
i_, inserted lamina; _m_, margin.]

The second kind, M. De Blainville terms the _lateral_ bivalves, the pieces
being placed in pairs on each side of the animal; these compose the
"Pedunculated Cirripedes."

[Illustration: Fig. 86, Anatina.]

They differ considerably in the number and arrangement of the valves; the
small ones, which are found near the peduncle in some species, are
sometimes termed accessary valves; those which form the edge through which
the bunch of Cilia protrude, are termed _ventral_, and those on the
opposite side _dorsal_. The extremity joining the peduncle is the basal, or
anterior; and the upper extremity is the apsiral, or posterior. The
peduncle is the medium of attachment to submarine substances, to which this
well known tribe of shells adhere.

The third kind are termed _coronular_ by De Blainville, and compose the
order Sessile Cirripedes of Lamarck; they consist of a number of valves
placed against each other side by side in a circle, supported on a plate,
or tube, or cup, and closed by an operculum composed of two or more valves.

The _basal support_ is sometimes thick and flat, sometimes forming an
elongated tube, and sometimes hollowed out into a cup. In other species it
is altogether wanting. The operculum always consists of more than one
piece, generally of two pairs: they are either articulated to each other by
serrated edges, and placed against each other conically, as in Balanus, or
they lie flat in two pairs against each other. Through the ventral pair the
_cirrhi_ protrude.

The _parietal_ valves, composing the principal part of the shell, vary in
number, form and position. The _anterior_ valves are placed on the same
side with the cirrhi; the _posterior_, those on the opposite side; and
those which remain between on each side are the lateral valves. In many
cases, particularly in Balanus, each valve is separated into the
_prominent_ and _depressed_ areas, and the inserted lamina. In some
instances, the parietal portion is formed by a single rounded piece.

[Illustration]

In the accompanying cut (87), the prominent areas are distinguished by the
letters _pr_, and the depressed areas by _r_; the posterior valves of the
operculum are marked _p. o._, and the anterior _a. o._ The basal valve
(fig. 88) belongs to a Balanus. Fig. 89 is an Acasta, the cup-shaped base
of which is represented at fig. 90.

In the foregoing explanations we have omitted many of those general terms
which, relating to external characters, are applicable to shells in almost
every division of the system. It may be as well, however, to enumerate a
few of them in this place, although they are explained under their
respective letters in the alphabetical part of the work.

When bars or ribs, or large striæ are crossed by others radiating from the
umbones, shells are said to be _cancellated_, as represented in cut, fig.
91. When there is a series of nodules or spines on the upper part of the
whorls, they are _coronated_, as shewn in cut, fig. 92. When a series of
projecting parts overlay each other, in the manner of tiles, as in the cut,
fig. 93, the word _imbricated_ is applied. When marked by a regular series
of ridges, radiating from the apex, they are _pectinated_; the species of
Chiton, a single valve of which is represented in cut, fig. 94, has
received the specific name of _pectinatus_, in consequence of this
character. Shells are said to be _plicated_ when characterized by angular
bendings or foldings in their surface, as shewn in cut, fig. 95. A strong
instance of this is seen in the Ostræa Crista-Galli. When the margin of any
shell has a series of minute notches, resembling the teeth of a saw, it is
said to be _serrated_; when covered with raised points or spines it is
_aculeated_; and when striated in both directions, it is _decussated_; when
covered with a number of raised rounded points, it is _granulated_; and
having a series of these points placed in a row, near or upon the edge, it
is _denticulated_, as already explained in reference to the outer lips of
Spiral Univalves. When the external surface is rendered uneven by raised
knobs, it is said to be _tuberculated_; and if rendered rough and prickly
by sharp points it is _muricated_, as in the cut, fig. 97. The term
_reticulated_ is applied to fine raised lines, crossing each other, and
resembling fine net-work.

[Illustration: External surface. Fig. 91, _cancellated_; 92, _coronated_;
93, _imbricated_; 94, _pectinated_; 95, _plicated_; 96, _decussated_; 97,
_muricated_; 98, _foliated_.]

By the foregoing general observations and explanations, it is trusted that
the reader will be prepared for the following exposition of the general
arrangement of Lamarck, and the principles upon which it is founded.

       *       *       *       *       *

GENERAL ARRANGEMENT

ACCORDING TO LAMARCK.

In Lamarck's "Histoire Naturelle des Animaux sans Vertebres," he divides
the invertebrata into classes, the 9th, 10th, and 11th of which include
animals possessed of shells properly so called. These are the ANNELIDES,
the CIRRIPEDES, the CONCHIFERA, and the MOLLUSCA.

The class ANNELIDES constitutes the 9th, and is divided into three orders,
namely, the "Apodes," "Antennees," and "Sedentaires"; the last of which,
_Sedentaria_, alone contains testaceous animals. This order includes
tubular shells, which, with the exception of Dentalium, are irregularly
twisted, and attached to each other, or to extraneous substances. The first
family _Dorsalia_, contains the genus Siliquaria (plates, fig. 1), known
from the Serpulæ, by the slit which passes through the whole length of the
shell on the upper surface of the tube. The second family, _Maldania_, has
the genus Dentalium (plates, fig. 2), a species of which are commonly known
by the name of "tooth shells"; these are regularly formed, curved conical
tubes, open at both extremities. The third family, _Serpulacea_, includes
the genera Serpula, Spirorbis, Galeolaria, Vermilia, Spiroglyphus, and
Magilus. The only shell that a learner would be likely to place among these
incorrectly, according to the system, is the Vermetus (plates, fig. 345),
which being regularly spiral at the apicial extremity, has been placed
among the Mollusca; to which situation the whole of the shells under
consideration have a better title than is generally supposed. It should be
mentioned that the Serpulacea are provided with opercula.

Class CIRRIPEDES.

This class constitutes the tenth of invertebrated animals, and receives its
name from the jointed and ciliated branchia which protrude between the
opercular valves. They are Multivalve shells, and were all included in the
single genus Lepas in the system of Linnæus, and are commonly known by the
name "Barnacles." Lamarck has, however, divided them into two distinct
orders. First, the _Sessile_ Cirripedes or those which being composed of
several valves, joined to each other, side by side in a circle, are
attached to each other, or to submarine bodies by the basal portion of
their own substance, and form a hollow, irregular cone, with the aperture
above closed by an operculum consisting of two or more valves. Secondly,
the _Pedunculated Cirripedes_, which are composed of valves placed in pairs
against each other, so as to form a flattened disc attached by means of a
tendinous tube called a peduncle. The first of these orders includes the
genera Tubicinella, Coronula, Platylepas, Clitia, Conia, Elmineus,
Catophragmus, Octomeris, Balanus, Creusia, Nobia, Savignium, Pyrgoma, Adna,
Megatréma. The second contains the genera Pentelasmis, Scalpellum, Smilium,
Pollicipes, Bisnæus, Lithotrya, Ibla, Octolasmis, Cineras, Otion.

Conchological writers are not agreed as to the propriety of allowing the
above to enter into the present science.

Class CONCHIFERA.

The shell of a conchiferous animal is always bivalve, composed of two
pieces placed opposite to each other, joined at the dorsal margins by an
elastic hinge. All true bivalve shells belong to animals of this class; and
the correspondence between the shell and the animal is so true that on
examining an empty bivalve shell we can not only determine that its
inhabitant belonged to this class, but also decide on the particular order
and family in which it should be placed, without seeing the soft parts.

The first general division of Conchifera is that which results from
observing the muscular impressions, or marks made on the inner surface of
the valve by the insertion of the adductor muscles. All Conchifera are
divided into two orders, as follows:

First Order, _Conchifera Dimyaria_.

Having two adductor muscles, and consequently two impressions in each
valve. They are separated into the following families:

    1. _Tubicolæ_ (plates, fig. 44 to 54), having shelly tubes besides the
    valves. This family contains the genera Aspergillum, Clavagella,
    Teredina, Teredo, Xylophaga, Fistulana, and Gastrochæna.

    2. _Pholadaria_ (plates, fig. 55 to 59), cylindrical, living in holes
    in rocks pierced by the animals. Lamarck places in this family the
    genera Pholas and Gastrochæna, the last of which belongs more properly
    to the family Tubicolæ, as placed above.

    3. _Solenacea_ (plates, fig. 60 to 68), longitudinally (transversely,
    Lam.) elongated, open at the anterior and posterior extremities. This
    family contains the genera Solen, Pholadomya, Panopæa, Glycimeris
    (Solecurtus) and Solenimya.

    4. _Myaria_ (plates, fig. 69 to 76), ligament internal. A spoon-shaped
    ligamentary pit in one or both valves. Shell generally gaping at one or
    both extremities. This family includes the genera Anatina, Mya,
    Anatinella, Lyonsia, Myochama, Cleidotherus.

    5. _Mactracea_ (plates, fig. 77 to 88), the cartilage placed in a
    trigonal pit, with a small external ligament. The genera Lutraria,
    Mactra, Crassatella, Erycina, Ungulina, Amphidesma, and Solenimya
    belong to this family, the last of which ought to have been placed
    among the Solenacea, as above.

    6. _Corbulacea_ (plates, fig. 89, 90), inequivalve, with an internal
    ligament resembling the Mactracea, but differing in having one valve
    deeper than the other, although regular shells. This small family
    contains only the genera Corbula and Pandora.

    7. _Lithophagidæ_ (plates, fig. 91 to 97), irregular, terebrating,
    living in holes of rocks. The genera are Saxicava, Petricola, and
    Venerirupis.

    8. _Nymphacea_ (plates, fig. 98 to 110), ligament external, generally
    placed upon a prominent fulcrum, which passes from the inside to the
    outside of the hinge; valves generally gaping at the extremities. This
    family contains the genera Sanguinolaria, Psammobia, Psammotæa,
    Tellinides, Corbis, Lucina, Donax, Capsa, and Crassina.

    9. _Conchacea_ (plates, fig. 111 to 121), regular, having several
    cardinal teeth and sometimes lateral teeth. The Conchacea constitute
    one of the most beautiful and numerous families of the class; they
    present equivalve shells, which are always regular, unattached, and in
    general closed, especially at the sides; they are always more or less
    inequilateral. They are divided into the _fluviatile_ and _marine
    Conchacea_, the first containing the genera Cyclas, Cyrena, and
    Galathæa, found in rivers; and the second, Cyprina, Cytherea, Venus,
    and Venericardia.

    10. _Cardiacea_ (plates, fig. 122 to 130). This family, which resembles
    the last in some general characters, are also regular and equivalve,
    and are generally provided with radiating ribs, which are seldom seen
    in the Conchacea. The genera enumerated in this family are Cardium,
    Cardita, Cypricardia, Hiatella, and Isocardia.

    11. _Arcacea_ (plates, fig. 131 to 138). These are known by having a
    row of numerous small teeth on the cardinal hinge in each valve. The
    genera included are, Cucullæa, Arca, Pectunculus, Nucula.

    12. _Trigonacea_ (plates, fig. 139 and 140). It is doubtful whether
    this family should remain distinct. As of the two genera placed in it,
    the first, Trigonia, is thought by some naturalists to have strong
    affinities with Nucula, in the family of Arcacea; and the latter,
    Castalia, certainly belongs to the Nayades.

    13. _Nayades_ (plates, fig. 141 to 152). These are fresh-water shells,
    covered on the outside by a thick horny epidermis, and pearly within.
    They include the genera Unio, Hyria, Anodon, Iridina.

    14. _Chamacea_ (plates, fig. 153 to 155), inequivalve, irregular,
    foliaceous, attached; containing the genera Diceras, Chama, and
    Etheria.

Second Order, _Conchifera Monomyaria_.

Having one adductor muscle, and therefore only one impression in each
valve. They are separated into the following families:--

    1. _Tridacnacea_ (plates, fig. 156 & 157), transverse, equivalve, with
    an elongated muscular impression, near the centre of the ventral
    margin; margin undulated at the termination of the radiated large ribs.
    The genera Tridacna and Hippopus are included.

    2. _Mytilacea_ (plates, fig. 158 to 162), generally regular, with the
    hinge linear, without teeth, occupying the greater part of the dorsal
    margin. This family includes the genera Modiola, Mytilus, Pinna.

    3. _Malleacea_ (plates, fig. 163 to 170), shell generally thin,
    inequivalve, irregular, foliaceous, with the hinge linear. This family
    contains the genera Crenatula, Perna, Malleus, Avicula, Meleagrina.

    4. _Pectinides_ (plates, fig. 171 to 178). The Pectinides are generally
    regular or nearly so, with the shell solid; the greater part of them
    are auriculated at the dorsal margin, and generally characterized by
    ribs radiating from the umbones. The genera are Pedum, Lima,
    Plagiostoma, Pecten, Plicatula, Spondylus, Podopsis.

    5. _Ostracea_ (plates, fig. 180 to 192). The shells of this family are
    irregular, generally attached and foliaceous. They compose the genera
    Gryphæa, Ostræa, Vulsella, Placuna, Anomia.

    6. _Rudistes_ (plates 193 to 200). This family is composed of a
    particular association of shells, which appear on one side to be
    connected with the Ostracea; and on the other to approach the
    Brachiopoda. They differ from Ostracea in having no hinge or ligament,
    and only resemble them in their irregularity and foliaceous structure.
    The following six genera are placed by Lamarck in this
    family:--Sphærulites, Radiolites, Calceola, Birostrites, Discina,
    Crania. Of these, Calceola, Discina, and Crania are shewn to belong to
    the Brachiopoda.

    7. _Brachiopoda_ (plates, fig. 201 to 219). The shells of this family
    are inequivalve, equilateral, and attached to marine bodies by a tendon
    passing through one of the valves. The animals have, near their mouth,
    two elongated, ciliated arms, which are spirally rolled when at rest.
    The following genera are enumerated by Lamarck, Orbicula, Terebratula,
    Lingula.

MOLLUSCA.

Lamarck applies, or rather restricts, this name to those invertebrated
animals, which while they are inarticulate in all their parts, have the
head sufficiently advanced at the anterior part of the body to be
distinguished; which is not the case with the Conchifera. All the shells
are univalve, and are divided into six orders, namely, the PTEROPODA, which
have wing-shaped natatory organs or fins, and have _light_, _thin
transparent_, _nearly symmetrical_ shells; the GASTEROPODA, with the foot
not distinguishable from the rest of the body, have _patelliform_, _open_,
and _scarcely spiral_ shells; the TRACHELIPODA with the foot distinct and
attached to the neck of the animal, have _spiral_, _non-symmetrical_
shells. The CEPHALOPODA, with arms covered by suckers surrounding the head
of the animal, have generally _symmetrical convolute_ shells. The
Cephalopoda are divided into _C. polythalamia_, which have the internal
cavity divided into chambers by septa, as in the Nautilus; and the _C.
Monothalamia_, which are not so divided, as the Argonauta. The order
_Heteropoda_ contains the genus Carinaria alone.

Order _Pteropoda_.

This order, containing hyaline, symmetrical, non-spiral shells, as above
described, is not divided into families, but contains the following genera,
Hyalæa, Cleodora, Limacina, Cymbulia; the first of which, although composed
of a single piece, resembles a bivalve so nearly, that Linnæus actually
placed it in his genus Anomia.

Order _Gasteropoda_.

With the exception of the genus Bulla and Vitrina, the last of which forms
a passage into the next order, the shells contained in this order are
_patelliform_, _open_, _and scarcely spiral_. They are divided into the
following families:--

    1. _Phyllidiana_ (plates, fig. 227 to 231), containing the genera
    Chiton, Chitonellus, and Patella, the two former of which present the
    only exception to the statement above made, that all the shells of
    Mollusca were univalve.

    2. _Semiphyllidiana_ (plates, fig. 232 and 233). Of the two genera
    contained in this family, Pleurobranchus is broad, thin, and slightly
    spiral at the apex, and Umbrella is flat, circular, with a central
    apex.

    3. _Calyptracea_ (plates, fig. 234 to 246). The patelliform shells of
    this family, although united by no other general characters, are
    brought together by the characters of the animals which produce them.
    The genera are Parmophorus, Emarginula, Siphonaria, Fissurella,
    Pileopsis, Calyptræa, Crepidula, Ancylus.

    4. _Bulleana_ (plates, fig. 247 to 253), contains the genera Bulla and
    Bullæa.

    5. _Aplysiacea_ (plates, fig. 254 and 255). The genera Aplysia and
    Dolabella are both expanded, somewhat flattened shells, with the apex
    placed at one extremity, and slightly spiral.

    6. _Limacinea_ (fig. 256 to 263). Many of the animals (slugs) are
    without shells; some, as the Limax, or common garden slug, have a
    slightly developed calcareous piece, hidden beneath the mantle, and of
    others the shells are scarcely spiral. The genera included in this
    family are, Parmacella, Limax, Testacella, Vitrina.

Order _Trachelipoda_.

All the remaining spiral non-symmetrical shells are arranged in this order,
which is divided into the following families:--

    1. _Colimacea_ (plates, fig. 264 to 307). With the exception of the few
    contained in the family of Limacina, which ought not to be separated
    from this order, the whole of the land-shells are contained in this
    family, and although it is difficult to notice any one character by
    which terrestrial shells may be distinguished from others, few at all
    conversant with the subject are liable to mistake them. There is a
    general lightness and simplicity of form, which, though not clearly
    definable, is generally understood. The following distribution of
    genera by Lamarck, is generally acknowledged to require numerous
    modifications; the genera are Helix, Carocolla, Anostoma, Helicina,
    Pupa, Clausilia, Bulinus, Achatina, Succinea, Auricula, Cyclostoma.

    2. _Lymneana_ (plates, fig. 308 to 312). The shells of this family are
    found in fresh water, wells, ditches, and ponds. They are of a light
    horny structure, and simple form. The genera Planorbis, Physa, and
    Lymnea are placed in this family by Lamarck.

    3. _Melaniana_ (plates, fig. 313 to 317). These are also found in fresh
    water, principally in rivers; they are thicker than those of the last
    family; and the greater part of them have elevated spires composed of
    numerous whorls. This family contains the genera Melania, Melanopsis,
    Pirena.

    4. _Peristomata_ (plates, fig. 318 to 322). These are also fresh-water
    shells, having opercula, and covered by a smooth green, or
    greenish-brown epidermis. They differ from the last family in having
    the peritreme entire. The genera are Valvata, Paludina, and Ampullaria.

    5. _Neritacea_ (plates, fig. 323 to 333). The peculiarity of the shells
    of this family consists in the inner lip being flattened and rather
    straight at the inner edge. The genera are Navicella, Neritina, Nerita,
    Natica, and Janthina, the last of which forms an exception to the
    general character, and is placed by De Blainville in a family by
    itself.

    6. _Macrostomata_ (plates, fig. 334 to 341), so named, on account of
    the large open aperture which they present in comparison to the spire.
    The shells of this family, which contains the genera Stomatia,
    Stomatella, and Haliotis, are pearly within.

    7. _Plicacea_ (plates, fig. 342 to 344), contains the genera Tornatella
    and Pyramidella.

    8. _Scalariana_ (plates, fig. 345 to 352). The genera Vermetus,
    Scalaria and Delphinula, seem to have been placed in this family by
    Lamarck, on account of the whorls being distinct from each other.

    9. _Turbinacea_ (plates, 353 to 371). The shells contained in this
    family are all more or less globose, or angular, thickened and pearly
    within. The following genera are included in this division by Lamarck,
    Solarium, Rotella, Trochus, Monodonta, Turbo, Planaxis, Phasianella,
    and Turritella.

    10. _Canalifera_ (plates, fig. 372 to 401). The numerous genera of
    which this family is formed, namely, Cerithium, Pleurotoma, Turbinella,
    Cancellaria, Fasciolaria, Fusus, Pyrula, Ranella, Murex, Triton, are
    distinguished by having at the anterior termination of the aperture, a
    more or less elongated canal.

    11. _Alatæ_ (plates, fig. 402 to 406). These are known by having the
    outer lip more or less expanded and generally a posterior canal leaning
    towards the spire. The genera are Rostellaria, Strombus, and
    Pteroceras.

    12. _Purpurifera_ (plates, fig. 407 to 429). In these, the canal, if
    such it may be called, is extremely short, and turning abruptly
    backwards, produces a kind of varix at the lower part of the whorl. The
    genera enumerated in this family are Cassidaria, Cassis, Ricinula,
    Purpura, Monoceras, Concholepas, Harpa, Dolium, Buccinum, Eburna,
    Terebra.

    13. _Columellata_ (plates, fig. 430 to 433). The shells of this family
    are emarginated at the anterior extremity of the aperture, and the
    inner lip is characterized by plates or folds, which, with the
    exception of those on Columbella, are distinct. The genera are Mitra,
    Voluta, Marginella, Volvaria, Columbella, the latter of which would be
    better placed among the Purpurifera.

    14. Convolutæ (plates, fig. 444 to 462). The well-known shells
    contained in this family are distinguished for the small proportion of
    the spire, if any, which remains uncovered by the last whorl. They
    might be well divided into two groups, the first containing the genera
    Ovulum and Cypræa, under the name of Cypræadæ, which are truly
    convolute, having the spire entirely hidden; and the second containing
    the genera Oliva. Ancillaria, and Conus.

Order _Polythalamous, or Chambered Cephalopoda._

The greater part of the shells belonging to this order are symmetrical, and
the internal cavity is divided into separate compartments, by plates called
_Septa_. It is divided into the following families:--

    1. _Orthocerata_ (plates, fig. 463 to 470), containing the genera
    Belemnites, Orthoceras, Nodosaria, Hippurites, and Conilites.
    Hippurites certainly has no affinity with the Cephalopoda, but is
    ascertained to be a bivalve shell, properly belonging to the family
    Rudistes; the other genera are straight, elongated, and conical.

    2. _Lituacea_ (plates, fig. 471), containing the genera Spirula,
    Spirulina, and Lituola, the two latter of which are microscopic.

    3. _Cristacea_, containing the microscopic genera Renulina, Orbiculina,
    and Cristellaria.

    4. _Spherulacea_, containing the microscopic genera Miliola, Gyrogona,
    and Melonia.

    5. _Radiolacea_, containing the microscopic genera Rotalites,
    Lenticulina, Placentula.

    6. _Nautilacea_ (plates, fig. 472 to 476). This family contains the
    following genera--Discorbites, Siderolites, Polystomella, Vorticialis,
    Nummulites, and Nautilus; the two latter of which alone are now
    received in cabinets of shells, the four former belonging to that class
    of microscopic fossils, now termed Foraminifera; the genus Nummulites,
    although large, may probably belong to the same class, and perhaps it
    would have been better to have included the remaining genus, Nautilus,
    in the next family, from which it differs in having the septa which
    divides the chambers simple at their edges.

    7. _Ammonacea_ (plates, fig. 477 to 484). The edges of the septa of
    these are all more or less sinuous and complicated. This family
    contains the following genera, Ammonites, Ammonoceras, Baculites, and
    Turrilites, the latter of which presents a singular anomaly in having
    an oblique spire, like that of the order Trachelipoda, while it is
    divided into chambers by sinuous septa.

Order _Monothalamous Cephalopoda_.

The only shells included in this order belong to the genera Argonauta
(plates, fig. 485), placed here by Lamarck, and Bellerophon (plates, fig.
486 and 487), a fossil genus subsequently added.

Order _Heteropoda_.

The singular and beautiful transparent shell contained in this order, under
the generic name Carinaria, forms a covering to a small portion of an
animal, equally remarkable and equally distinct from those of all other
orders.



The above arrangement, although far from perfect, and requiring numerous
modifications, is perhaps liable to as few objections as any other yet
proposed, and will certainly be more easily understood by those who have
not the opportunity of studying the soft parts of the animal.

       *       *       *       *       *

CONCHOLOGICAL MANUAL.

    ABIDA. Leach. A genus founded on a species of PUPA, which has the
    peristome slightly reflected, and numerous plaits in the aperture. Pupa
    Juniperi, Pupa secale, Draparnaud. Great Britain; also Central and
    Southern Europe.

    ABRA. Leach. A genus composed of AMPHIDESMA tenue, prismaticum, and
    other small thin species. British Channel and Mediterranean. _Fam._
    Mactracea.

    ABSIA. Leach. LITHOTRYA, Sowerby. _Fam._ Pedunculated Cirripedes.

    ACAMAS. Montfort. BELEMNITES multiforatus, Blainville. A species
    described as being perforated at the apex, by a stellated perforation.
    No species of Belemnite at present known agreeing with the description;
    it is supposed to have been taken from a broken specimen.

    ACANTHOCHETES. A name given to a species of Chiton having bunches of
    bristles at the sides of the valves.

    ACARDO. Commerçon. Described from a pair of bony plates, taken from the
    vertebræ of the Whale, and mistaken for a bivalve shell, destitute of a
    hinge.

    ACARDO. Swainson. A generic term applied by Swainson to the nearly
    toothless species of Cardium, named C. edentulum by some authors; C.
    Greenlandicum by others: fig. 123*.

    ACASTA. Leach. _Order_, Sessile Cirripedes, _Lamarck_. BALANUS
    _Montagui_, Sowerby. A small genus separated from Balanus, on account
    of the cup-shaped base, but re-united by Sowerby, who shews, in his
    Genera of Shells, that this is a merely accidental circumstance,
    resulting from the situations in which the shells acquire their growth.
    If, for instance, the Balanus be attached to a flat surface, in an open
    situation, the base will be short and flat; if it be placed in a hollow
    among other growing substances, it will be lengthened out in order that
    the aperture of the shell may be even with the outer surface of the
    surrounding mass; and if, as in the Acastæ, it be imbedded in a soft
    and loose substance, the base, being left to itself, will take a
    regular form. The Acastæ are found imbedded in sponges. _Ex._ Balanus
    Montagui, of Great Britain, fig. 26. Also found in the Pacific ocean
    and Philippines.

    ACAVUS. Montfort. _Fam._ Limacinea, Blainville; Colimacea, Lamarck. A
    division of the genus Helix, which may be considered synonymous with De
    Ferrusac's sub-genus Helicogena. De Montfort has given H. Hæmastoma, as
    an example. Fig. 267.

    ACCESSARY VALVES, are the smaller or less important testaceous plates,
    found on the hinge or dorsal margins of the true valves of some shells.
    Example, the small plates on the hinge of Pholas, fig. 55, a. The
    Pholades were placed by Linnæus and Bruguière among multivalve shells.

    ACEPHALOPHORA. Blainville. (_a_, without; [Greek: kephale], head.) The
    third class of the type Malacozoaria, Bl. including all bivalve shells,
    the animals of which have no distinct head. This class corresponds with
    the Conchifera of Lamarck, and is divided into the orders
    Palliobranchiata, Rudistes, Lamellibranchiata, and Heterobranchiata,
    the last of which contains no genera of testaceous Mollusca.

    ACHATINA, Auctorum. _Fam._ Colimacea, Lam. (from Achates, an agate.)
    _Fam._ Limacineæ, Bl. _Gen._ POLYPHEMUS, Montf.--_Descr._ Shell oval or
    oblong, sub-turrited, light, thin; aperture oval, or pyriform; outer
    lip sharp; columella smooth, tortuous, truncated, so as to form a notch
    at its union with the outer lip.--_Obs._ It is from this notch that we
    are enabled to distinguish Achatinæ from Bulini, which, moreover,
    generally have a reflected outer lip. The Polyphemi of Montfort have an
    undulation in the centre of the outer lip. Achatina Virginea, fig. 286.
    Polyphemus Glans, fig. 288. These land shells are found in various
    parts of the globe, but attain the greatest size and richness of
    colouring in tropical climates; particularly in the West India Islands.

    ACHATINELLA. SOW. A small group of shells, differing from Achatina in
    having the inner edge of the outer lip thickened, and a slight groove
    near the suture of the spire. Fig. 287. Sandwich Islands.

    ACHELOIS. Montf. CONILITES Achelois. Knorr. Supp. T. 4, fig. 1.

    ACICULA. Nilson. ACHATINA Acicula, Auct. CIONELLA, Jeffreys.

    ACIONA. Leach. A genus described by De Blainville as consisting of
    those species of Scalaria, the whorls of which do not touch each other.
    If this account be correct, the genus proposed by Leach will include
    the typical species of Scalaria, such as S. pretiosa.

    ACME. Hartmann. A genus formed of TURBO fuscus, Walker. AURICULA
    lineata, Drap. thus described--"Shell sub-cylindrical, with a blunt
    tip; mouth ovate, simple, thin, slightly reflected over the pillar,
    forming a slight perforation." The animal is said to resemble a
    Cyclostoma, but has no operculum. Auricula lineata, Drap. Hist. 57, t.
    3, fig. 20, 21. Southern Europe.

    ACTEON. Montf. TORNATELLA, Lam.

    ACTINOCAMAX. Stokes. A genus of Belemnitiform Fossils.

    ACULEATED. Beset with sharp spines, as the margin of Chiton aculeatus,
    fig. 227.

    ACUMINATED. Terminating in a point, as the apex of Melania subulata,
    fig. 313.

    ACUS. Humphrey. TEREBRA of Lamarck.

    ACUTE. Sharp, pointed, or sharp-edged.

    ADDUCTOR MUSCLE. That which draws the two valves of a shell together,
    and leaves a mark on the inner surface of each, called the MUSCULAR
    IMPRESSION.

    ADELOSINA. D'Orb. A genus of microscopic Foraminifera.

    ADESMACEA. Bl. (_a_, without; [Greek: Desma], _desma_, ligament.) The
    10th family of the order _Lamellibranchiata_, Bl. composed of Mollusca
    which either bore tubular dwellings in rocks, wood, &c. or live in
    testaceous tubes, their shells being consequently destitute of the
    hinge ligament. The action of opening and shutting the valves being
    limited to the narrow space to which they are confined, or else the
    valves themselves being soldered into the tube, renders it unnecessary
    for them to have a ligament to keep them in their places. The genera
    Pholas, Teredina, Fistulana, and Septaria, belong to this family, which
    corresponds in part with the families Tubicolaria and Pholadaria, of
    Lamarck.

    ADNA. Leach. One of the genera separated by Leach from _Pyrgoma_, and
    characterized as consisting of an upper valve, supported on a
    funnel-shaped base, which is not buried in the coral to which it is
    attached, like Pyrgoma, but is seen externally. The operculum consists
    of four valves. Adna, fig. 32. British Channel and Mediterranean.

    ADNATE. A term applied by some authors to those shells belonging to the
    family of Unionidæ, which have the valves joined together at the dorsal
    margin, not like other bivalves, by a distinct ligament, but by the
    substance of the shell itself, the valves appearing to grow together in
    such a manner that they cannot be separated without one of them being
    broken as will be seen in our figure of Dipsas plicatus, fig. 142. This
    circumstance has been made the foundation of specific and even generic
    distinctions, for which however it is insufficient, because many
    species which when young are "_adnate_," when fully grown have their
    valves joined together only by a ligament.

    ÆGLIA. Say. A division of "Unionidæ," described as having the "shell
    cuneate; bosses prominent; cardinal teeth much compressed, placed on
    one side of the bosses. Æglia ovata, _Say_. Occidens _Lea_. Am. Tr.
    iii. pl. 10." Lardner's Encyclopedia of Malacology.

    AGANIDES. Montf. ORBULITES, Lam.

    AGATHIRSES. Montf. SILIQUARIA, Auct.

    AGINA ----? Belongs to SAXICAVA, Auct.

    AKERA. Bl. The fourth family of the order Monopleurobranchiata, Bl.
    containing the genera Bulla, Bullæa and Bellerophon, which, excepting
    the last, constitutes the family Bullæana, Lam.

    AKERA. A genus of extremely light, horny shells, resembling BULLA, from
    which it differs, in the outer lip being separated from the body whorl,
    which is elastic. _Ex._ Bulla fragilis, fig. 247.

    ALÆA. Jeffrey's. A genus of minute land shells, resembling _Vertigo_,
    but separated because they are dextral, while Vertigo is sinistral.
    _Ex._ fig. 292. A. marginata, Pupa marginata, Drap. found in marshy
    ground, roots of trees, moss, &c. Britain and Southern and Central
    Europe.

    ALASMODON. Say. A division of the genus UNIO, Auct. consisting of those
    species which have cardinal, but no lateral teeth. _Ex._ A.
    complanatus, fig. 141. North America and Europe.

    ALATÆ. Lam. A family of the order Trachelipoda, Lam. containing the
    following genera which may be thus distinguished.

        1. ROSTELLARIA. Sinus close to the canal; including _Hippochrenes_,
        and _Aporrhais_, Fig. 402 to 404.

        2. STROMBUS. Sinus not close to the canal. Fig. 406.

        3. PTEROCERAS. Same, digitated. Fig. 405.

    ALATED. (From Ala, a wing.) Winged, a term applied to shells, when any
    portion of them is spread out in any direction, as in fig. 403.
    Hippochrenes, Montf. and fig. 147, Unio Alatus.

    ALCADIA. Gray? (B. M. Syn. p. 134) Helicinæ which have a notch in the
    aperture. A distinction which it is impossible to maintain. See
    HELICINA.

    ALATUS. Humphrey. STROMBUS, Auct.

    ALECTRION. Montf. BUCCINUM Papillosum, Auct. fig. 422.

    ALEPAS. Rang. A genus of Pedunculated Cirripedes without a shell.

    ALVEOLINA. D'Orbigny. A genus of microscopic Foraminifera.

    AMALTHUS. Montf. A. margaritaceus, Montf. is a species of AMMONITES
    described as very flat, keeled, with an angular aperture. It belongs to
    the family Ammonacea, Lam.

    AMARULA ----? A genus composed of MELANIA Amarula, Auct. and similar
    species.

    AMBIGUÆ. Lam. The fourth section of the order Conchifera Dimyaria,
    containing the family Chamacea, fig. 153 to 155.

    AMICULA. A genus formed for the reception of CHITON amiculatus, Auct.
    the valves of which are covered by an integument; so as to be
    completely hidden externally.

    AMIMONUS. Montf. CONILITES ungulatus, Knorr. A species distinguished
    only by being slightly curved; _Fam._ Orthocerata, Lam.

    AMMONACEA. Bl. The fourth family of the order Polythalamia, Bl. or
    chambered shells, described as thin, chambered, discoidal, convolute,
    symmetrical, generally compressed, with visible whorls. This last
    character is used in De Blainville's System to distinguish the
    Ammonacea from the Nautilacea. This family contains the genera
    Discorbites, Scaphites, Ammonites, and Simplegas.

    AMMONACEA. Lam. The seventh family of Polythalamous Cephalopoda, Lam.
    containing the genera Ammonites, Orbulites, Ammonoceras, Turrilites and
    Baculites, to which may be added Amalthus, Simplegas, Ellipsolites,
    Nautellipsites, Hamites, Icthyosarcolites, and other genera mentioned
    in the list of figures 477 to 484.

    AMMONITES. Auct. (from Jupiter Ammon.) _Fam._ Ammonacea, Lam. and
    Bl.--_Descr._ Symmetrical, convolute, discoidal, orbicular; chambers
    numerous, divided by lobated, branched or sinuous septa, perforated by
    a Siphon; aperture generally more or less modified by the last whorl.
    The fossils of the secondary strata which compose this genus are
    numerous and well known; they are vulgarly termed "snake-stones," and
    some of them are extremely beautiful, particularly when the internal
    structure is exhibited by a section. There is some difficulty in
    distinguishing them from the Fossil Nautili, for although the whorls,
    being visible and the Septa _sinuous_, may be taken as the
    characteristics of the Ammonites, yet there are several species which
    partake the characters of both. The Orbulites of Lamarck (fig. 479) for
    instance, have sinuous septa like Ammonites, but the last whorl covers
    those which precede it as in Nautilus. Simplegas Montf. and Bl. (fig.
    475) has the whorls visible externally and the septa simple. Ammonites
    is figured in the plates (478).

    AMMONOCERAS, or AMMONOCERATITES. Lam. (from _Ammon_ & [Greek: Keras],
    ceras, horn.) The shells described under this Lamarckian genus present
    an anomaly which is considered by Mr. G. B. Sowerby, sen., as merely
    accidental. They resemble the Ammonites in internal structure, but
    instead of being spirally convolute they are merely curved like a horn.
    _Ex._ fig. 477, copied from De Blainville.

    AMNICOLA. The name of a genus mentioned in the family of Melaniana in
    the conchological part of the Synopsis of the British Museum, but
    unexplained.

    AMPHIBOLA ----? The same as AMPULLARIA, Auct.

    AMPHIBULIMA. Lam. SUCCINEA Patula, Auct. (fig. 266.) was first
    published in the Ann. du. Mus. D'Hist. Nat. under the name Amphibulima
    cucullata. The generic name was afterwards abandoned by its author, and
    the species stands in his system as Succinea cucullata. West Indies.

    AMPHIDESMA. Lam. (from [Greek: Amphô], _ampho_, _ambo_, [Greek:
    Desmos], _desmos_, _ligamentum_). _Fam._ Mactracea, Lam.--_Descr._
    Equivalve, oval or rounded, sub-equilateral, sometimes rather gaping at
    the sides, with slight posterior fold; hinge with one or two cardinal
    teeth in each valve, and two elongated lateral teeth, distinct in one
    valve, nearly obsolete in the other; ligament short, separated from the
    cartilage, which is elongated and couched obliquely in an excavation of
    the hinge.--_Obs._ In most bivalve shells, the cartilage and ligament
    are united in one mass, or placed close to each other; the contrary in
    this case gives rise to the name, which signifies _double ligament_.
    This circumstance distinguishes the genus Amphidesma from Tellina,
    which in other respects it greatly resembles. From Lutraria it may be
    known by its distinct lateral teeth, and also by its valves being
    nearly close all round, while the Lutrariæ gape anteriorly. The species
    do not appear to be numerous, no fossil species are known. A.
    _Reticulatum_, fig. 85. West India Islands, Brazil, Coast of Pacific,
    &c.

    AMPHIPEPLEA. Nilson. The type of this proposed genus is LIMNEA
    glutinosa, Auct. Gray's edition of Turton, page 243, plate 9. fig. 103.
    The shell is polished and the inner lip expanded.

    AMPHISTEGINA. D'Orb. A genus of microscopic Foraminifera.

    AMPLEXUS. J. Sowerby. A. _Corralloides_, fig. 463. A singularly formed
    fossil, described as nearly cylindrical, divided into chambers by
    numerous transverse septa, which embrace each other with reflected
    margins. It occurs in the Dublin limestone, and resembles a coral or
    madrepore.

    AMPLEXUS. A generic name proposed by Captain Brown for HELIX pulchella,
    Drap. 112, tab. 107-134. Zurama, Leach.

    AMPULLARIA. Auct. (_Ampulla_, a rounded vessel). _Fam._ "Peristomiens,"
    Lam. Ellipsostomata, Bl.--_Descr._ Spiral, globular, sometimes
    discoidal, frequently umbilicated, covered with a rounded, horny
    epidermis; spire short; whorls rapidly enlarging; aperture elliptical,
    rounded anteriorly; peristome nearly or quite entire, thickened and
    slightly reflected; operculum, testaceous, annular, with a subcentral
    nucleus.--_Obs._ This genus of fresh-water shells of which a few fossil
    species occur, is easily distinguished from other genera, by obvious
    characters, particularly by a thick, horny, greenish-brown epidermis,
    and the rotundity in form. One species, the A. Cornu-arietis which
    forms the type of Lamarck's genus Planorbis, requires notice on account
    of its flatness, but may be known by the aperture which in the
    Ampullaria is longer than wide, and in Planorbis the contrary.
    Lanistes, Montf. is described from a _reversed_ species of Ampullaria.
    The Ampullaria is vulgarly called the Idol Shell, and is said to be
    held in great veneration by the South American Savages. The animal has
    a large bag, opening beneath, placed on the side of the respiratory
    cavity. It is supposed that the animal has the power of filling this
    bag with water, and that it is thus enabled to live a long time out of
    water. They have been brought as far as from Egypt to Paris alive,
    packed in saw-dust. _Ex._ fig. 318. East and West Indies, North Africa,
    South America, &c.

    AMPULLARINA ----? A genus formed for the reception of AMPULLARIA
    avellana. Fig. 538. From Australia.

    AMPULLINA ----? Part of the genus HELICINA, Auct.

    ANALOGOUS. A term applied to certain species of fossil shells, which
    present a certain degree of resemblance to recent species; but which
    are not sufficiently similar to warrant the use of the term
    'identical,' or any other implying that they are of the same species.

    ANASTOMA or ANOSTOMA. Fischer. (from [Greek: Ana], _ana_, backwards;
    [Greek: Stoma], _stoma_, mouth) _Fam._ Colimacea, Lamark. A genus of
    land shells so named from the singular circumstance of the last whorl
    taking a sudden turn and reflecting the aperture upwards, so as to
    present it on the same plane with the spire; so that the animal walks
    with the spire of the shell downwards resting on the foot. In other
    respects, the two species of which this genus is composed, resemble
    other Helices; and belong to De Ferrusac's division "Helicodonta."
    _Tomogerus_ is De Montfort's name for this genus. _A. depressum_ is
    represented in the plates figs. 271, 272. The nearest approach to this
    genus will be found in the fossil shell named Strophostoma, by
    Deshayes, which, however, has no teeth in the aperture and is provided
    with an operculum like Cyclostoma. South America.

    ANATIFER. Brug. ANATIFA, Lam. This name, which signifies Duckbearing,
    has been given to the shells commonly called Barnacles, on account of
    an absurd notion entertained among the ancients, that they inclose the
    young of the Barnacle duck, in an embryo state. The beautiful bunch of
    jointed arms, the ciliæ of which serve the purpose of agitating the
    water, so as to draw in food by the current, were supposed to be the
    feathers of the future bird. For a description of these shells, see
    PENTELASMIS; and fig. 34.

    ANATINA. Lam. (_That which belongs to a duck._) _Fam._ Myaria, Lam.
    Pyloridea, Bl.--_Descr._ Thin, transparent, generally equivalve,
    inequilateral, transverse, marine; hinge with a spoon-shaped process in
    each valve, containing the cartilage.--_Obs._ Some species included in
    the genus Anatina of authors, A. striata, for instance, have not the
    spoon-shaped prominence, but in its place a small, testaceous, moving
    appendage, connected with the interior of the hinge. These are now
    separated, and form the genus LYONSIA. The genus Næara, Gray, is
    composed of Anatina longirostrum, and similar species, which have
    neither the bony appendage nor the spoon-shaped prominence. Mya is
    distinguished from Anatina, by the thickness of the shell, and also by
    having the prominence only in the hinge of one valve. Fig. 69. A.
    rostrata. The Anatinæ are found in the East Indies and South Sea
    Islands.

    ANATINELLA. G. B. Sowerby. (Dimunition of _Anatina_). A genus so named
    from its resemblance to Anatina, from which it differs in being
    destitute of the internal appendage, and having no sinus in the palleal
    impression. One species having been brought from Ceylon, received the
    name of Anatinella Sibbaldii. Another has lately been found in the
    Philippine Islands. Fig. 70.

    ANATOMUS. Montf. Tom. 2, plate 279. A microscopic shell, appearing from
    the figure to resemble SCISSURELLA.

    ANAULAX. Brogn. ANCILLARIA, Auct.

    ANCILLA. Lam. ANCILLARIA, Auct.

    ANCILLARIA. Auct. ANCILLA, Lam. (_A handmaid._) _Fam._ convolutæ, Lam.
    Angyostomata, Bl.--_Descr._ Smooth, oblong, subcylindrical. Spire
    short, sutures hidden by enamel. Aperture long, anteriorly emarginated
    and somewhat effuse. Columella tortuous, oblique, tumid,
    truncated.--_Obs._ The Ancillariæ are pretty shining shells, enveloped
    almost entirely by the soft parts of the animal. They resemble Oliva,
    from which they are distinguished by the suture of the spire being
    filled up with shelly enamel, nearly covering the surface. The whorls
    in Oliva being separated by a distinct canal. Ancillaria may be known
    from Terebellum by the tumid varix at the base of the columella. The
    well known Ivory shell, Eburna glabrata, _Lam._ belongs to this genus,
    of which a few fossil species are found in the London clay, Calcaire
    grossièr and green sand, Turin. The recent species are found in the
    Islands of the Indian Ocean and Australian Seas. A. glabrata is
    represented in the plates fig. 455; A. cinnamonea, fig. 456.

    ANCULOSA. Say. _Fam._ Melaniana, Lam. Ellipsostomata, Bl. A genus
    proposed to include some fresh-water shells resembling those of the
    genus Melania, the difference between them being that the spire of
    Anculosa is more depressed, and the anterior of the outer lip more
    angulated than in Melania. On an examination of the different species,
    however, it will be found that this is quite unsatisfactory, as a
    generic distinction; because some of the species with short flattened
    spires, have rounded, and others angulated apertures. North America. An
    example of each is represented, fig. 314.

    ANCYLUS. Geoffroy. _Fam._ Calyptracea, Lam. Otides, Bl.--_Descr._ Thin,
    obliquely conical, patelliform; apex acute, turned sidewise and
    backwards; aperture oval; margin simple.--_Obs._ Although the little
    fresh-water shells described under this name, resemble those of the
    genus Patella, the animals which produce them are nearly allied to the
    Lymneanæ. And, it may also be observed, that the shells themselves
    differ from Patella in not being quite symmetrical, having the apex
    turned on one side. A. fluviatilis, fig. 246. Found in Great Britain,
    and in Southern and Central Europe, West Indies, &c.

    ANDROMEDES. Montf. VORTICIALIS, Lam. _Fam._ Nautilacea, Lam. A genus of
    microscopic Foraminifera.

    ANGULATED. (Angulatus.) Having an angle, or corner, as the anterior of
    the aperture of Eulima, fig. 348; the posterior side of Castalia, fig.
    140; the whorls of Carocolla, fig. 277.

    ANGULITES. Montf. A genus composed of species of fossil NAUTILI,
    described by De Blainville as not umbilicated, with a dorsal keel and
    angular aperture. NAUTILUS triangularis Buffon.

    ANGIOSTOMATA. Bl. The third family of Siphonobranchiata, Bl. described
    as differing little from the family of Entomostomata, but having long,
    narrow, straight apertures, and the columellar lips straight or nearly
    so. Were it not for the admission of the genus Strombus into this
    family, it would correspond with COLUMELLARIA and CONVOLUTÆ of Lamarck.

    ANNELIDES. The ninth class of invertebrated animals, divided into three
    orders, namely, A. Apodes, A. Antennés, and A. Sedentaires. The last
    only contains families of testaceous Mollusca. The animals are
    vermicular, some naked, others inhabiting shelly tubes. See SEDENTARY
    ANNELIDES.

    ANNULAR OPERCULUM is one which has the nucleus central, or nearly so,
    the other layers surrounding it in flattened rings. The term concentric
    is also applied. See Introduction.

    ANNULATED. (Annus, a ring.) Composed of, or surrounded by rings, as in
    the case of Tubicinella, fig. 14.

    ANODON. Brug. _Fam._ Submytilacea, Bl. Nayades, Lam. A genus composed
    of such species of NAYADES as are destitute of teeth on the hinge.
    Europe, North America, &c. An example is given in A. Cataractus, fig.
    152.

    ANOMALINA. D'Orb. A genus of microscopic Foraminifera.

    ANOMIA. _Fam._ Ostracea, Lam. and Bl.--_Descr._ Irregular, inequivalve,
    sub-equilateral, foliaceous, pearly within; adhering to marine
    substances by means of a bony appendage, which passes through a large
    circular opening in the lower valve; muscular impression divided into
    three irregular portions; hinge destitute of teeth with a short
    cartilage.--_Obs._ The Linnæan genus included not only the shells to
    which the description above given would apply, but also many other
    genera, such as Crania, Orbicula, Terebratula, &c. which belong to the
    Brachiopoda, and are perfectly distinct. The Anomiæ are found in
    Europe, N. America, Moluccas, Philippine Islands, &c. Fig. 186, in the
    plates, is a somewhat reduced representation of a full grown specimen
    of A. Ephippium. Fig. 187, the hinge of the under valve, with the bony
    process. Fig. 188, the hinge showing the opening through which it
    passes.

    ANOSTOMA. See ANASTOMA.

    ANSATES. Klein. A genus formed of those species of Patella which have a
    produced, recurved beak. Helcion, Montf. _Ex._ Patella pellucida, fig.
    230.

    ANSULUS or ANSYLUS. Mr. Gray conjectures that the name of the genus
    Ancylus, should be so written.

    ANTENOR. Montf. A genus of microscopic Foraminifera.

    ANTERIOR. In Bivalves is the side on which the head, or part analogous
    to the head of the animal lies; it is known in the shell by the
    umbones, which if turned at all, are turned towards that part. If there
    be a sinus in the impression of the mantle, it is always on the
    posterior part of the shell. If the ligament be placed only on one side
    of the umbones, it is only on the posterior side. The anterior of a
    _spiral univalve_ is that part of the outer lip which is at the
    greatest distance from the apex. Of a _symmetrical_ conical univalve
    such as Patella, it is that part where the head of the animal lies,
    indicated by the interruption of the muscular impression. Of
    _cirripedes_, that part where the ciliæ protrude are anterior; of
    _Brachiopoda_, that part which is farthest from the umbones and which
    corresponds with the ventral margin in other Bivalves. The anterior of
    _symmetrical, convolute univalves_, is the outer or dorsal part of the
    aperture, or that part which is farthest from the spire. Lamarck and
    other Conchological writers have occasioned much confusion by their
    errors on this subject; describing the same part of a shell at one time
    anterior, at another posterior; but generally the reverse of the above
    arrangement, which is founded upon the natural position of the animal,
    and generally adopted. The anterior will be indicated by the letter
    _a_, in figs. 119, 421, 229, 34, 202.

    ANTIGONA. Schum. A genus composed of VENUS cancellata, Lam. (fig. 119.)
    and similar species.

    ANTIQUATED. This word, signifying _out of date_, is occasionally used
    to express that species of composition which constantly occurs in
    shells, by each fresh deposit or layer of calcareous matter, forming a
    new margin, which being replaced by its successor, is no longer used as
    the margin, and is consequently said to be out of date.

    APEX. This term does not apply to the natural position of a shell, but
    is used in a mathematical sense, to indicate the nucleus or first
    formed part; which may be considered as the point of the spiral cone.
    From this point, the shell enlarging rapidly or slowly as it descends,
    takes a spiral, arched, straight, oblique, convolute, or irregularly
    spiral course. The apex will be indicated by the letter _a_, in fig.
    282 and 466.

    APERTURE or MOUTH. The entrance to the spiral cavity of univalve
    shells. The parts of the aperture are separately described, as follows:
    The inner lip or labium is that part which lies over the preceding
    whorl of the shell. It terminates anteriorly, or towards the lower part
    in what is termed the columella, so called because it forms a kind of
    axis on which the volutions turn. The outer lip, sometimes called the
    labrum, is on the opposite side, or the farthest from the axis. If the
    edges of the inner and outer lips unite all round, they are described
    as composing the peritrême. In fig. 318, the aperture is marked by the
    letter a.

    APHRODITA. Lea. (from [Greek: Aphroditê], Greek name of Venus.) A genus
    composed of CARDIUM Groenlandicum, Auct. fig. 123*, and other similar
    species of Cardium, the teeth of which are either wholly wanting, or
    very indistinct. Northern Ocean.

    APICIAL. Belonging to the apex. The apicial extremity of the aperture
    of a univalve shell, is that which is nearest to the apex of the spire.

    APICULUM. Humph. TROCHUS, Lam.

    APLEUROTIS. Rafinesque. A genus unfigured and imperfectly described as
    differing in some respects from Terebratula and other Brachiopodæ.

    APLEXUS. Fleming. A genus composed of PHYSA Hypnorum, Drap. &c. and
    described as having the inner lip simple, and not spread over the body
    whorl.

    APLODON. Rafinesque. A genus proposed to be established at the expense
    of the genus HELIX, but upon what grounds does not appear from the
    imperfect description which is unaccompanied by a figure.

    APLUSTRE. Schum. A genus formed for the reception of those species of
    BULLA which have the spire uncovered. _Ex._ Bulla Aplustre,
    (_aplustre_, a flag.) Auct. fig. 289.

    APLYSIA. Linn. (_a_, without; [Greek: Pluô], to wash.) _Fam._
    Laplysiens, Lam. Aplysiana, Bl.--_Descr._ Horny, transparent,
    clypeiform, or shield-shaped, placed horizontally on the back of the
    animal, with its convex side uppermost; apex slightly incurved.--_Obs._
    The animal producing this shell has derived its name from the purplish
    liquor which it exudes, when disturbed. In contour, it has been fancied
    to present a certain likeness to a hare crouching, and on this account
    was called _Lepus marinus_, or sea hare, by the ancients. The shell
    bears a strong resemblance to Dolabella, which, however, is much
    thicker, and more testaceous. The species are found in the
    Mediterranean, European, and West Indian Seas. A. Petersoni, fig. 254.

    APLYSIACEA. Bl. The second family of the order Monopleurobranchiata,
    Bl. The animals composing this family are either destitute of shells,
    or are provided with internal ones, which are flat, open, oblique, with
    the apex or nucleus slightly incurved, not distinctly spiral. This
    family contains the genera, Aplysia and Dolabella. The first
    sub-spiral, with the apex terminal; shell thin, horny. Fig. 254. The
    second the same, but thick and shelly. Fig. 255.

    APOLLON. Montf. RANELLA Ranina, Auct. Placed by De Blainville in that
    division of Ranella, which is characterized as being umbilicated. Fig.
    393.

    APOROBRANCHIATA. Bl. The first order of the second section of
    Paracephalophora Monoica, Bl. The Thecosmata is the only family of this
    order containing any approach to shells, these are Hyalæa and Cymbulia.

    APORRHAIS. Petiver. A genus formed of ROSTELLARIA Pes-pelicani, _Auct._
    (fig. 404) and similar species. Although the shell presents no
    characters to distinguish it generically from Rostellaria, those who
    have examined the soft parts are convinced that it is distinct. Of the
    three species now known and figured in part I. of Thesaurus
    Conchyliorum, by the Author, one is common on our own coast, and in the
    Mediterranean; also North America. See ROSTELLARIA.

    AQUATIC. A term applied by some authors to those species of Molluscous
    animals, which inhabit fresh water, either in rivers, or salt water
    standing pools, as distinguished from the marine or Mollusca. See
    Fresh-water.

    AQUILLUS. Montf. TRITON Lampas, Cutaceus, &c. Auct. Placed by De
    Blainville in the division of the genus Triton, which is described as
    having a short spire, being covered with tubercles and umbilicated.
    Triton Cutaceus, fig. 399.

    ARCA. Auct. (Anglicè, a boat.) _Fam._ Arcacea, Lam.--_Descr._ Obliquely
    transverse, subquadrate, equivalve, or nearly so, inequilateral, thick,
    ventricose, longitudinally ribbed, dentated near the inner margins;
    hinge rectilinear, forming a flat, external area, upon which the
    ligament is spread in cross rows, and having a series of small, regular
    teeth, extending on both sides of the umbones in each valve; muscular
    impressions distant.--_Obs._ The shells composing this genus are easily
    distinguished from those of all other bivalve shells, by the straight,
    linear row of small, notched teeth, and by the area between the
    umbones. The genus _Cucullæa_ makes the nearest approach to it in this
    respect, but it may easily be known from it by the outermost teeth on
    each side of the row being oblique, and lengthened out; and also by the
    prominent edge of the muscular impression. These shells are found
    recent, in various marine localities; fossil, in the tertiary deposits.
    The Arca Noæ, formerly regarded as the type of this genus, has, with
    several other species, been separated from it under the name of
    Bysso-arca, by Swainson, on account of an hiatus in the ventral margin,
    to admit the passage of a byssus; this is not found in the true Arcæ.
    The true Arcæ are mostly tropical. Arca Antiquata, fig. 131. Bysso-arca
    Noæ, 132.

    ARCACEA. Lam. A family of the order Conchifera Dimyaria, characterized
    by a series of teeth placed on the hinge in a line. The genera may be
    distinguished as follows,

        1. ARCA. Hinge straight; valves close. Fig. 131.

        2. BYSSO-ARCA. Valves gaping. Fig. 132.

        3. CUCULLÆA. Distant teeth oblique; posterior muscular impression
        prominent. Fig. 133.

        4. PECTUNCULUS. Hinge curved. Fig. 134.

        5. NUCULA. The same, with a pit in the centre of the hinge,
        including Myopara and Crenella. Figs. 135 to 137.

        6. SOLENELLA. Fresh water, oval; a series of teeth on one side of
        the hinge, only two or three on the other. Fig. 138.

    ARCHAIAS. Montf. A genus of microscopic Foraminifera.

    ARCHONTE. Montf. HYALÆA, Auct.

    ARCINELLA. Schum. CHAMA Arcinella, Auct.

    ARCTICA. Schum. CYPRINA Icelandica, Auct.

    ARCUATED. (Arcus, an arch.) Bent in the form of an arch, as Dentalium,
    fig. 2.

    AREA. A flat space or disc, on any part of a shell. As for instance,
    the triangular space on the hinge of Arca, fig. 132, and Spondylus.

    ARENACEOUS. (Arena, sand.) Of a sandy texture, as the sand tubes
    surrounding the bodies of some of the Annellides, named Arenaria on
    this account. But the word is more commonly used to intimate the habits
    of the animal, burrowing with its shell in the sand.

    ARETHUSA. Montf. A genus of microscopic Foraminifera.

    ARGONAUTA. Auct. Commonly called the "Paper Sailor." _Fam._ Pteropoda,
    Bl. _Order_ Cephalopoda Monothalamia, Lam.--_Descr._ Light, thin,
    transparent or nearly so, symmetrically convolute, carinated by a
    double row of tubercles, terminating smooth or tuberculated ribs
    radiating towards the centre; aperture large, elongated; peritrême
    acute, interrupted by the body whorl.--_Obs._ The exquisitely
    beautiful, light and delicate fabrics included under the above name are
    inhabited by a molluscous animal named the _Ocythöe_, which is provided
    with tuberculated arms. These, hanging over the sides of the aperture,
    give to the whole the appearance of a vessel propelled by oars: a
    poetical illusion further heightened by the broad, flat membranes of
    the two arms, which, when vertically expanded, present an idea of
    sails. Pliny has described the Nautilus (the name has been changed by
    the moderns) as sailing gracefully on the Mediterranean waters; and
    Pope has versified the idea in the well known lines

        "Learn of the little Nautilus to sail, Spread the thin oar and
        catch the driving gale."

    Scientific men have long been engaged in the interesting discussion,
    whether the animal really belongs to the shell in which it is found, or
    whether, having destroyed the rightful owner, it has possessed itself
    of the "frail bark." It is now, however, proved beyond the shadow of a
    doubt that the Argonaut is the testaceous part of the Ocythöe, and that
    the broad membranes which in some representations have been
    artificially placed as sails, are naturally bent backwards over the
    shell like the mantle of some other molluscs. The interesting
    experiments of Madame Power, in the Mediterranean, have contributed
    very materially to lead the investigations of Naturalists to a
    satisfactory conclusion. This lady kept a cage under water, in which
    Argonautæ were bred in great numbers, giving her an opportunity of
    tracing the gradual development of the shell in all its stages, from
    the elastic and transparent nucleus to the full grown "Paper Sailor."
    Fig. 485.

    ARIANTA. Leach. A sub-genus of land shells, containing HELIX
    arbustorum, Auct. (Gray, Turton, p. 137.)

    ARION. A genus of slugs which have no shells.

    ARROW-HEADS. One of the names by which fossils of the genus Belemnites
    were formerly known.

    ARTEMIS. A genus of bivalve shells, distinguished from those of the
    genus Venus, by having a rounded, denticular form, and a deep, angular
    sinus in the palleal impression. This does not appear to me to be a
    sufficient ground of generic distinction, the palleal impressions of
    the Veneres being subject to great variations. British, also from West
    Indies, South America, Australia, &c. A. lincta, fig. 118.

    ARTICULATED. (Jointed.) Applied to distinct parts of shells, which are
    fitted or jointed into each other, as the valves of Chitones and those
    of Balani. The operculum of Nerita is said to be _articulated_ to the
    columella, having a small process by which it is as it were locked
    under the edge. See _Introduction_. The word is also applied to the
    Cirri, which protrude from the oral openings of Cirripedes.

    ARTICULINA. D'Orb. A genus of microscopic Foraminifera.

    ASIPHONIBRANCHIATA. Bl. The second order of Paracephalophora Dioica,
    Bl. Consisting of spiral univalves, which have no notch or canal at the
    anterior part of the aperture. This order is divided into the families
    Goniosomata, Cricosomata, Ellipsostomata, Hemicyclostomata, and
    Oxystomata.

    ASPERGILLUM. Lam. (From _Aspergo_, to sprinkle.) _Fam._ Tubicolæ, Lam.
    Pyloridea, Bl.--_Descr._ The small, equal, equilateral valves are
    cemented into, so as to form part of, a large tube; the umbones are
    slightly prominent outside. The tube is elongated, rather irregular,
    granulated with sandy particles, and terminated at the base by a convex
    disc, which is perforated by small pores, elongated into tubes round
    the edge, presenting a resemblance to the spout of a watering pot,
    whence the name is derived. _Loc._ New Holland, Java, New Zealand, Red
    Sea. Fig. 44. Aspergillum Vaginiferum.

    ASSIMINEA. Leach. _Fam._ Turbinacea, Lam.--_Descr._ Inclining to oval,
    light, thin, covered with a horny epidermis, spire produced into an
    acute pyramid; whorls slightly angulated in the centre, rounded
    beneath; aperture elliptical, slightly modified by the last whorl;
    inner lip planed; outer lip thin; operculum horny, subspiral. Found in
    brackish water; one species may be procured abundantly on the muddy
    shores of the Thames, in Kent. There are also species from Calcutta,
    China, Tahiti, and Australia. Without comparing the animals, it is
    difficult to distinguish this genus from some species of Littorina.
    Fig. 363. A. Grayana.

    ASTACOLUS. Montf. A genus of microscopic Foraminifera. CRISTELLARIA
    Crepidula, Lam.

    ASTARTE J. Sowerby. (Name of a Sidonian Goddess, _Ashtaroth_ in
    Scripture.) _Fam._ Nymphacea, Lam. Genus Crassina, Lam.--_Descr._
    Suborbicular, equivalve, inequilateral, thick, compressed; hinge with
    two solid diverging teeth in the right valve, one tooth and a slight
    posterior elevation in the left; muscular impressions, two in each
    valve, uniform, united by a simple palleal impression; ligament
    external.--_Obs._ This genus differs from Venus, Cytheræa, &c. in not
    having a posterior sinus in the impression of the mantle. The hinge
    also differs in having but two cardinal teeth. Astarte differs from
    Crassatella in having no internal cartilage in the hinge. Some of the
    species are British, others are from America, and one from Sicily. The
    fossils occur in Crag, Lower Oolite, &c. Fig. 110. A. Danmoniensis.

    ASTROLEPAS. Klein. CORONULA Testudinaria, Auct. CHELONOBIA, Leach. Fig.
    15.

    ATLANTA. Lesueur. _Fam._ Pteropoda, Lam. and Bl.--_Descr._ Spiral,
    convolute, transparent, fragile, compressed, with a broad, fimbriated,
    dorsal keel, and a narrow aperture. This shell, which is called "_corne
    d'ammon vivant_," is found in the Atlantic. The small Pteropod, figured
    in Sowerby's Genera as Limacina, belongs to this genus. Atlanta
    Helicialis, fig. 220.

    ATRACTODON. Charlesworth. (Mag. Nat. Hist. 2nd series, Vol. 1. p. 218.
    ) A genus proposed for the admission of a singular fossil shell, found
    on the beach at Felix-stone, of which the following are the
    characters;--fusiform, aperture equalling the spire in length,
    terminating anteriorly in a slightly recurved canal; columellar lip
    smooth, curved, thickened posteriorly into a blunt tooth; spire
    obtuse.--_Obs._ This shell would be a Fusus were it not for the tooth
    on the posterior extremity of the columellar lip. The only species
    known is regularly striated in a spiral direction, and named A.
    Elegans.

    ATRYPA, Dalman. A genus of brachiopodous bivalves, distinguished by the
    valves being nearly equal, and the umbones not separated by an
    intermediate area. A. reticulata, fig 302.

    ATTACHED. Shells are attached to marine substances by various means; in
    some cases by a _byssus_, or a bunch of tendinous fibres passing
    through an opening between the valves, which gape at their margins to
    admit a free passage, as in the genera Byssoarca and Mytilus. In other
    cases the byssus is of a more compact substance, and passes through a
    perforation in the shell itself. This is the case with many of the
    brachiopodous shells, in some species of which the perforation is in
    the point of the umbones, a specimen of which is represented in the
    Introduction. This species of attachment does not keep the animal
    motionless, although it is confined to a particular spot. Other shells
    are attached by a portion of their own substance, as in Chama,
    Spondylus, Serpula, &c. in which instances, the attached valve is
    motionless, and is termed the under valve. The Pedunculated Cirripedes
    are attached by a tubular tendinous process, called a peduncle.

    ATTENUATED. Drawn out, long, thin, tapering, as the extremities of
    Ovulum Volva, fig. 442.

    ATYS. Montf. A generic name including those species of BULLA, which are
    described as "convolute, with the last whorl covering the rest and
    hiding the spire, the apex rounded at both ends." Bulla Naucum, Auct.
    fig. 250.

    AURICLE. (A little ear.) See AURICULATED.

    AURICULA. Lam. (Dim. from _Auris_ an ear.) _Fam._ Auriculacea. Bl.
    Colimacea, Lam.--_Descr._ Oval or oblong, cylindrical or conical;
    aperture long, narrow, generally narrowest in the centre; rounded
    anteriorly, with two or three strong folds on the inner lip, and the
    outer lip thickened, reflected or denticulated; spire short, obtuse,
    epidermis horny, brown.--_Obs._ The above description includes the A.
    coniformis, f. 298. and several other conical species with narrow
    apertures which formed the genus _Melampus_, Montf. and _Conovulus_,
    Lam. The latter author suppressed his genus on ascertaining the
    Conovuli to be land shells. We exclude, however, the A. Dombeyana, Lam.
    f. 300. and several similar species, which being more rounded, having
    thin outer lips and but one fold on the columella, are described under
    the generic name _Chilina_, Gray. It appears rather doubtful whether
    the Auriculæ are marine or fluviatile, but the animals appear to be
    amphibious. The Auriculæ are principally found in Salt Marshes of
    Tropical climates, some small species are found on the Southern
    European Coasts, as far north as Britain and south as Tierra del Fuego.
    The Auriculæ formed a part of the genus Voluta of Linnæus, f. 297. A.
    Judæ, f. 298. A. Coniformis.

    AURICULATED. Some bivalve shells, such as _Pecten_, fig. 171, 172, have
    a flat, broad, somewhat triangular appendage on one or both sides of
    the umbones, called an _auricle_, or little _ear_. If on one side only,
    they are said to be _uni-auriculated_; if on both, they are said to be
    _bi-auriculated_.

    AURICULACEA. Bl. The second family of the order Pulmobranchiata, thus
    described; "shell thick, solid; aperture more or less oval, always
    large, rounded anteriorly, and contracted by teeth or folds on the
    columella." This family is included in the genus Voluta of Linnæus, on
    account of the plaited columellar lip, a character by which that
    heterogeneous assemblage of shells is distinguished. It forms part of
    the family of _Colimacea_, Lam. from which they differ not only in
    general form, but also in the fact of the animals being partly
    amphibious, always living (according to De Blainville) on the sea
    shore, and being occasionally covered with water for a short time. It
    contains the genera Pedipes, Auricula, Pyramidella.

    AURIFERA. Bl. OTION, Auct.

    AURIFORM. (From _Auris_, an ear; _forma_, shape.) Ex. _Haliotis_, fig.
    338.

    AURISCALPIUM. Megerle. ANATINA, Lam.

    AVICULA. Lam. (From _Avis_, a bird). _Fam._ Malleacea, Lam.
    Margaritacea, Bl.--_Descr._ Inequivalve, inequilateral, foliaceous,
    subquadrate, oblique, pearly; hinge rectilinear, lengthened into
    auricular appendages, with a small indistinct tooth in each valve, an
    elongated, marginal, ligamentiferous area, and an hiatus in the left
    valve, for the passage of a byssus; one circular muscular impression,
    near the centre of each valve, with a series of smaller ones arranged
    in a line towards the umbones.--_Obs._ The Meleagrinæ of Lamarck,
    Margaritiferæ, Schum. included in this description, consist of the more
    rounded species, and do not present the elegant obliquity of form, nor
    the wing-like auricles from which the genus Avicula receives its name.
    The Aviculæ are pearly within. From A. margaritifera, a young specimen
    of which is figured in the plates, fig. 164, is obtained oriental
    pearls. This is an example of Meleagrina. A. Hirundo, fig. 163, belongs
    to the genus Avicula of Lamarck. It is, however, needless to continue
    the separation. Aviculæ are from E. and W. Indies, Mexico, Coasts of
    the Pacific, Mediterranean, British Islands, &c. Fossil species occur
    in the London clay, &c.

    AXINUS. J. Sowerby.--_Descr._ Equivalve, transverse; posterior side
    very short, rounded, with a long ligament, placed in a furrow,
    extending along the whole edge; anterior side produced, angulated,
    truncated, with a flattish _lunule_ near the beaks. The late Mr. James
    Sowerby, who described this shell in the Mineral Conchology, did not
    consider his genus as established, not having seen the hinge.

    AXIS. The imaginary line, round which the whorls of a spiral shell
    revolve. The extremities of the axis are pointed out in fig. 379, by
    the letters, _a. a._ See "COLUMELLA."

    AZECA. Leach. _Fam._ Colimacea, Lam.--_Descr._ "Animal like Bulinus,
    with subcylindrical, rather obtuse shell, covered with a polished
    periostraca (epidermis); aperture pear-shaped, curved and pointed at
    the top; the margin thick, obtuse, united all round and toothed; the
    axis imperforated." Gray's edition of Turton's British Shells, page
    189.--_Obs._ The Turbo Tridens of Montagu, upon which this genus is
    founded, resembles Bulinus lubricus in general form and character. Both
    these shells differ from the true Bulini in having the peritreme
    entire, and in being pellucid and glossy. Azeca differs from Bulinus
    lubricus in having three teeth in the aperture, two on the inner lip
    and one on the outer. Not seeing the necessity for creating a genus on
    grounds so slight, I have simply transcribed the description given
    above, leaving others to form their own conclusions as to the propriety
    of separating this shell from the genus Bulinus. Britain, Central and
    Southern Europe. Azeca Tridens, fig. 290.

    AZEMUS. Ranzani. CONIA, Leach.

    BACULITES. Lam. _Fam._ Orthocerata, Bl. Ammonacea, Lam.--_Descr._
    Straight, conical, tubular, laterally compressed; chambers divided by
    very sinuous lobed septa, the last elongated; aperture elliptical;
    siphon dorsal.--_Obs._ This genus differs from Orthoceras in the same
    manner in which Ammonites differs from Nautilus, having its septa
    sinuated and branched. A Baculite might be described as a straight
    Ammonite. This genus is known only in a fossil state. It is found in
    the Cretaceous Limestone of Maëstricht and Valognes. Fig. 484. B.
    Faujasii.

    BALANUS. Brug. (an Acorn; "gland de Mer." Fr.) _Order_ Sessile
    Cirripedes, Lam. _Fam._ Balanidea, Bl.--_Descr._ Shell composed of six
    valves articulated to each other side by side in a circle, by the
    insertion of lamina; closed at the base by a flat, cylindrical or
    cup-shaped valve, by which it is generally attached; and at the apex by
    a conical operculum, consisting of four valves in anterior and
    posterior pairs. Each valve of the shell is divided into a rough
    triangular portion pointed towards the apex, and a flat area on each
    side.--_Obs._ This description includes the _Acasta_ of Leach, which
    growing in sponges, has the base cup-shaped; _Conoplæa_ of Say, which
    being attached to the stems of Gorgonia and sea-weeds has the base
    elongated and lanceolate, and _Chirona_, Gray. Balanus is the only
    genus of Sessile Cirripedes the shells of which consist of six parietal
    valves, except _coronula_, which has no shelly base, is flatter, and
    has the valves of the operculum placed horizontally. The Balani are
    common in all seas, adhering to rocks, corals, floating timber, and to
    each other. The fossil species are found in the newest strata, at
    Bordeaux, Paris, &c. Fig. 25. B. Tintinnabulum; 26. _Acasta_ Montagui;
    27. Balanus galeatus, _Conoplæa_, Say.

    BALANIDEA. Bl. The second family of the class Nematopoda, Bl.
    corresponding with Sessile Cirripedes, Lam., and consisting of
    Coronular Multivalves, which are fixed, and in a manner soldered to
    submarine substances, by the base of the shell; as distinguished from
    the Lepadicea, Bl., Pedunculated Cirripedes, Lam., which are attached
    by a fleshy stalk. The Balanidea are composed of two sets of valves,
    besides the shelly plate or base on which they rest. The first, called
    the Parietal valves, are arranged so as to surround the body of the
    animal; the second, called the Opercular valves, are placed
    horizontally, so as to cover the aperture.

    BALEA. Gray. _Fam._ Colimacea, Lam.--_Descr._ Spiral, turrited,
    concentrically striated, sinistral, and covered with a thin brown
    epidermis; spire composed of numerous whorls, gradually increasing in
    size; aperture small, sub-quadrate; peritrême entire, slightly
    thickened, with a very slight fold on the columella; axis
    perforated.--_Obs._ A genus of small land shells, found in moss at the
    roots of trees in Britain, not very nearly resembling any other land
    shells, except Clausilia, from which they differ in not having the
    clausium. They have been placed in Helix by De Ferrusac, and in Pupa by
    Draparnaud. B. fragilis, fig. 296. _Helix perversa_, Fer. _Pupa
    perversa_, Drap.

    BARBATA. Humphrey. UNIO, Lam.

    BARNACLES. PENTELASMIS, Auct. (fig. 34.) Called Anatifa, by Linnæus and
    Lamarck, from the ancient notion that they were the eggs or embryo of
    the Barnacle Duck. See ANATIFER.

    BASE. In all shells which are attached to sub-marine substances, the
    base is that part of the shell which forms the point of attachment,--as
    for instance, the attached valve of Spondylus, the basal plate of
    Balanus, the lower part of the peduncle of Pentelasmis; in Unattached
    Bivalves, the margin opposite to the umbones, where the foot of the
    animal, or the part analogous to it, protrudes; in spiral univalves,
    the aperture, which rests on the back of the animal when walking.
    Lamarck and some other authors have used the term _base_ as simply
    opposed to apex, and apply it to the anterior of the aperture.

    BATOLITES. Montf. HIPPURITES, Auct.

    BEAK. The Apices, or points of the valves of a bivalve shell, generally
    termed UMBONES, in descriptions. Also any part which is rostrated or
    drawn out like a beak.

    BEAKED. See BEAK and ROSTRATED.

    BEAR'S-PAW-CLAM. The common name for Hippopus maculatus, a
    representation of which is given in the plates, fig. 156.

    BELEMNITES. Auct. ([Greek: Belemnon], _belemnon_, a dart, or arrow.)
    _Fam._ Orthocerata, Bl. and Lam.--_Descr._ Straight, conical,
    consisting of two parts; the _external_ portion forming a thick solid
    sheath, with a cavity at the base to admit the internal portion or
    nucleus, which is mathematically conical, and is divided into chambers
    by smooth simple septa perforated by a lateral siphon.--_Obs._ These
    singular fossils, which are found in most secondary beds, have long
    attracted the attention of philosophers as well as of the ignorant,
    from whom they have received the various appellations of
    Thunder-Stones, Petrified Arrows, Petrified Fingers, Devil's Fingers,
    Spectre Candles, &c. The above description is framed to include the
    genera Hibolithes, Porodragus, Cetocis, Acamas, and Paclites of De
    Montfort, and Actinocamax, Stokes. Fig. 466 to 468.

    BELLEROPHON. Montf. (or Bellerophus).--_Descr._ Convolute, symmetrical,
    umbilicated, with a double dorsal ridge; aperture wide,
    semilunar.--_Obs._ The fossils composing this genus resemble Nautilus
    in general appearance, but not being chambered shells they approach
    very near to Argonauta, from which they differ only in the thickness of
    their shell and in roundness of their external form. This genus is
    erroneously placed by De Montfort among chambered shells, and by De
    Blainville next to Bulla. It belongs to the Monothalamous Cephalopoda
    of Lamarck. This fossil is found principally in the Carboniferous
    Limestone. Fig. 486, 487, represent B. tenuifasciata.

    BELOPTERA. The bony support of a species of Cuttlefish, partly
    resembling Sepia.

    BIAPHOLIUS. Leach. A genus believed to be identical with Hiatella.

    BI-AURICULATED. Having two auricles placed at the sides of the umbones,
    as in Pecten, fig. 171. See AURICULATED.

    BICATILLUS. Sw. A sub-genus of "Calyptrædæ," including those species,
    which have cup-shaped internal septa, as for example, Calyptræa
    extinctorium, fig. 235.

    BICONIA. Sw. A sub-genus of "Calyptrædæ," including those species in
    which the septum is partly spiral.

    BIFID. Divided, double.

    BIFRONTIA. Deshayes. Also OMALAXIS, Desh. _Fam._ Turbinacea,
    Lam.--_Descr._ Discoidal, planorbicular, with whorls sometimes not
    contiguous; umbilicus deep, keeled at the margin; aperture
    subtriangular, somewhat dilated; outer lip acute, separated by a deep
    notch at both extremities.--_Obs._ We do not see any reason for
    separating this genus from SOLARIUM, except the last mentioned
    character. The few fossil species which this genus contains (Solarium
    disjunctum, Bifrons, &c.) are found principally in the Paris basin.
    Fig. 354. Solarium Bifrons.

    BI-FURCATE. Double pronged, or having two points. _Ex._ the internal
    appendage of Calyptræa Equestris, fig. 234.

    BIGENERINA. D'Orb. A genus of microscopic Foraminifera.

    BILABIATED. Having the edge of the outer lip as it were doubled, by one
    part of the lip being more thickened and reflected than the other, so
    as to form a ledge, or second lip.

    BILOBATE. Having two prominent parts, as the outer lip of Rostellaria
    Pes-Peleeani, fig. 404.

    BIPARTITE. Composed of or divided into two parts; double; as the valves
    of Platylepas, fig. 19, each of which has a septiform division in the
    centre; also the area on the hinge of Spondylus. See Frontispiece.

    BIROSTRA. Sw. A genus composed of species of OVULUM, which have
    elongated extremities, as, for instance, Ovulum Volva, fig. 442.

    BIROSTRITES. Lam. (Double Beak.) A fossil formerly considered as a
    distinct bivalve shell, with conical umbones, and placed in the family
    of Rudistes by Lamarck, but now known to be an internal cast of
    Sphærulites, fig. 196.

    BISIPHYTES. Described by De Montfort as resembling a Nautilus, but
    having two distinct siphons. As no such fossil species is now known to
    Naturalists, it appears probable that De Montfort having a specimen of
    some Nautilus, with an accidental depression, took it for a second
    siphon.

    BITHINIA. Gray. A genus described as differing from PALUDINA, in having
    the operculum shelly, and the mouth of the shell thickened internally.
    PALUDINA impura, Auct. Fig. 537.

    BITOMUS. Montf. A microscopic shell, deriving this general appellation,
    from the appearance of a double aperture.

    BIVALVE. A shell composed of two equal, or nearly equal principal
    parts, each part having a separate nucleus, turning upon each other by
    means of a hinge. The class Conchifera of Lamarck, Acephalophora of De
    Blainville severally include the whole of the bivalve shells; the
    latter name being derived from the fact that the animals have not
    distinct heads, and neither eyes nor tentacula. All bivalve shells are
    marine or fresh-water. They form the class Dithyra of Aristotle. It may
    be observed that some of the Acephalophora, the Pholades, for example,
    have small testaceous pieces fixed on the hinge, which are called
    accessary valves. These are still fairly bivalve shells, although the
    genus Pholas has been placed by some writers among the multivalves.

    BOAR'S TUSK. A common name given to shells of the genus Dentalium. One
    particular species has received a specific name in accordance with a
    supposed resemblance, namely, Dentalium Aprinum, (of a Boar.)

    BONELLIA. Desh. A genus formed, in the first instance, for the
    reception of Bulinus terebellatus, Lam. which Mr. G. B. Sowerby, in his
    Genera of Shells, united with the genus PYRAMIDELLA. M. Deshayes,
    however, in his new edition of Lamarck, makes the genus Bonellia
    include several species which I have arranged in the genus Eulima. From
    the remarks of M. Deshayes, tom. 8, p. 286, 287, we are led to suppose
    that the estimated difference between Eulima and Bonellia consists in
    the latter having the axis perforated; or in other words, umbilicated.
    After remarking "que Mr. Sowerby, junr. confond deux choses bien
    distinctes, sous le nomme d'Eulima," M. Deshayes gives the following
    description of his genus, (translated) "shell turriculated, smooth,
    polished, with the apex acute and laterally inclined; axis perforated
    throughout its length; aperture small, entire, angular at the
    extremities; columella simple and without folds; outer lip thin,
    simple, nearly parallel with the longitudinal axis." That author
    further remarks, "Mr. Sowerby, junr. à signalé cinque espèces vivant,
    que nous rapportons à notre genre." (Sowerby, junr. Conchological
    Illustrations, parts 52 and 53; 50, Great Russell Street, Bloomsbury.)
    The species thus selected are E. splendidula, E. marmorata, E.
    interrupta, E. imbricata, E. brunnea; the two last of which have the
    umbilicus so inconsiderable, as to be scarcely distinguishable from
    other species, which M. Deshayes has left in the genus Eulima, and
    which have a slight hollow, almost approaching to a perforation, behind
    the columella. Eulima marmorata, (Bonellia, Desh.) is figured in the
    plates, fig. 348.

    BODY WHORL. The last whorl, constituting the bulk of the shell.

    BORELIS. Montf. MELONIA, Bl. A genus of microscopic Foraminifera.

    BORER or PIERCER. A term applied to those species of Acephalopodous
    Mollusca, which bore holes as dwellings in the rocks, as the Pholades,
    and some others.

    BRACHIOPODA. Lam. A family of symmetrical bivalves belonging to the
    third section of Lamarck's _order_ "Conchifera Monomyaria," described
    as bivalve (generally symmetrical) adhering to marine bodies, by a
    tendon passing through the shell, having no true ligament. What most
    distinguishes this family and renders it remarkable is the structure of
    the animal. It has two elongated, tendril-shaped arms. When the animal
    is in a state of repose these arms are coiled up spirally and enclosed
    in the shell, but when required for use, are unfolded and extended.
    This family contains the genera Orbicula, Terebratula and Lingula, in
    the system of Lamarck, to which may be added Thecidium, Productus,
    Spirifer, Magas, Pentamerus, Crania, Strigocephalus, Strophomena, and
    some others enumerated in the explanation of figures 201 to 219. The
    above genera may be thus distinguished.

        1. ORBICULA. Umbones central; byssus passing through a hole in the
        flat valve. Fig. 201.

        2. ATRYPA. Without foramen or space between the valves. Fig. 203.

        3. PRODUCTA. The same, valves produced, overwrapping; including
        Leptæna. Fig. 206, 206*.

        4. TEREBRATULA. Hinge of the upper valve produced beyond that of
        the other, with a pit or foramen; including _Delthyris_, _Orthis_,
        _Trigonosemus_, _Magas_, _Strophomena_. Fig. 202, 205, 207, 208,
        209.

        5. SPIRIFER. The same, with deep triangular area; spiral folds in
        the interior; including _Trigonotreta_ and _Cyrtia_. Fig. 204, 214,
        215.

        6. THECIDIUM. Large valve attached; curved ridges in the inner
        surface; two jutting points or teeth on the hinge. Fig. 216.

        7. CRANIA. Attached by the surface of the valve; muscular
        impressions four, forming a face. Fig. 197, _a_, b.

        8. PYCNODONTA. Irregular; hinge with raised pointed teeth. Fig.
        217, 218.

        9. PENTAMERUS. Valves divided by septa; including _Gypidia_. Fig.
        210 to 213.

        10. LINGULA. Valves equal, gaping, with a peduncle. Fig. 219.

    BRACHITOMA. Swainson. A genus composed of PLEUROTOMA strombiformis and
    similar species, described as "sub-fusiform; resembling a small
    Strombus or Fusus; spire and aperture of equal length; canal short;
    outer lip slightly ascending, and forming a short canal; sinus very
    small and nearly semicircular; inner lip thickened above. B.
    Strombiformis, Sow. Man. fig. 381." Europe, East and West Indies,
    China, &c.

    BRANCHIFERA. Bl. The second family of the order Cervicobranchiata,
    containing the following genera of symmetrical univalves:--Fissurella,
    Emarginula, and Parmophorus.

    BRISMÆUS. Leach. _Order._ Pedunculated Cirripedes. Lam.--_Descr._ Seven
    plates, three pairs lateral, one dorsal; form cylindrically conical;
    pedicle not described. _Hab._ Holes in corals. B. Rhophodius, fig.
    38.--_Obs._ This minute shell most nearly resembles Pollicipes
    Mitellus, fig. 37*, but the difference may be seen at once by comparing
    the figures.

    BRONTES. Montf. This generic name is given to such species of MUREX as
    have a very long, closed canal; with a short spire, circular aperture,
    and are destitute of spires and ramifications. Brontes (Murex)
    Haustellum, fig. 390.

    BUCARDIA. Schum. ISOCARDIA, Auct.

    BUCCINUM. Linn. _Fam._ Purpurifera, Lam. Entomostomata, Bl.--_Descr._
    Subovate or oblong, covered with an epidermis; spire turrited,
    consisting of few whorls; aperture wide, subovate, terminating
    anteriorly in a very short canal, reflected over the back; outer lip
    simple, slightly reflected; inner lip spread over a portion of the body
    whorl, terminating in a thick, smooth columella; operculum horny.
    _Hab._ British Seas, Northern Ocean, and Coast of Africa. Most of the
    fossil species occur in Crag, some in upper marine formation and London
    clay.--_Obs._ There are considerable difficulties in keeping this genus
    distinct from others nearly related to it, into which many of the
    species run by imperceptible gradations. The genus _Nassa_ has been
    separated on account of the little notch, which terminates the
    columella. Some species of Terebra come so close upon the Buccina, that
    it is difficult to say where one genus ends and the other begins. T.
    Buccinoides, fig. 427. Buccinum Undatum, the common Whelk, fig. 421.

    BUFO. Montf. A generic division of the species composing Ranella,
    characterized as having the shell not umbilicated. _Ex._ R. ranina,
    fig. 394. The above character is scarcely sufficient in some cases,
    even as a specific distinction.

    BULBUS. Humph. RAPELLA, Swainson. A genus formed for the reception of
    PYRULA papyracea, Auct. (fig. 389), and similar species. RAPANUS,
    Montf.

    BULIMIMA. Montf. A genus of microscopic Foraminifera.

    BULIMULUS. Leach. _Fam._ Colimacea, Lam. The author is unacquainted
    with the characters by which the two or three species included in this
    genus are to be distinguished from Bulinus. We have represented, fig.
    283, Bulimulus trifasciatus, Leach, (Bulinus Guadaloupensis, Auct.)
    This occurs in the same limestone which encloses the half fossilized
    human remains from the Grand Terre of Guadaloup. Several species are
    described by the Rev. L. Guilding in the Zoological Journal, namely,
    the B. Undulatus, Antiguensis, and Proteus; but neither from the shells
    themselves, nor from the figures of the animal, can we draw any
    information as to the generic character; the difference alleged by Mr.
    Swainson and Mr. Gray being a comparative thinness in the outer lip.

    BULINUS. Brug. (Bulinus, Lam.) _Fam._ Colimacea, Lam. Limacinea,
    Bl.--_Descr._ Oval or oblong, light, covered with a thin epidermis;
    spire obtuse, variable in length and in the number of whorls, which are
    generally few; aperture wide, oval, rounded anteriorly; outer lip
    simple, usually reflected, joining the columella without a sinus; inner
    lip reflected over part of the body-whorl. The Bulini are land shells,
    found in many parts of the world.--_Obs._ The genus Bulinus can only be
    distinguished from Helix by its oval form; it forms part of the genus
    Helix of De Ferrusac, under the sub-generic designation of Cochlostyla.
    It is known from Achatina by the absence of the notch at the point of
    union between the inner and the outer lips. The young are produced from
    eggs, which are as firm and opaque as those of birds. (See
    Introduction.) Bulinus rosaceus, fig. 282. B. Guadaloupensis, fig. 283.
    B. Lionetianus, fig. 284. B. lubricus, fig. 285. Many new species were
    brought to this country by Mr. Cuming, and are represented in the
    Conchological Illustrations, published by the Author at 50, Great
    Russell Street, Bloomsbury, (in parts 21, 22, 23, 26, 27, 30, 31, 34,
    35, 137 to 146, 185, 186.) Species occur in Europe, West Indies,
    Brazil, and South America generally. Some small species are British.

    BULLA. Auct. _Fam._ "Bulléens," Lam. Akera, Bl.--_Descr._ Generally
    thin, smooth, oval, oblong or cylindrical, more or less convolute;
    spire short, depressed, or hidden by the last whorl; aperture long,
    wide in front, gradually narrowing towards the spire; outer lip thin;
    inner lip spread over a part of the last whorl.--_Obs._ The shells
    composing this genus are very variable in form. The light horny species
    with an elastic lip is called Akera, fig. 247. The more decidedly
    convolute species with hidden spires are the Atys, Montf. B. Naucum,
    fig. 250. B. Lignaria, fig. 251, is Scaphander of Leach. The light,
    thin species, with extremely wide aperture, fig. 248, is Bullæa aperta,
    Lam. The genus Bullinula of Dr. Beck, consists of those species which
    have more produced spines, fig. 253. The Bullæ are marine, and inhabit
    all climates. The fossil species occur in tertiary beds.

    BULLÆA. Lam. BULLA aperta, Auct. fig. 248.

    BULLÆANA. ("Bulléens, Lam.") A family belonging to the first section of
    Lamarck's order, Gasteropoda, containing the genus Bulla. The genera
    Bullæa, Akera, Aplustra, Atys, Scaphander, Bullinula, into which it has
    been divided, may all be fairly included under the name BULLA.

    BULLIA. Gray. A genus of shells partly resembling Buccinum, and Terebra
    in general form, being more elongated than the former and more
    ventricose than the latter. Mr. Gray remarks in the Synopsis of the
    British Museum, page 114, that the Bulliæ resemble the Nassæ in most
    characters, "but they have a very large, broad foot, and the hinder
    part of the inner lip of the shell being extended beyond the mouth,
    forms a raised enamelled band round the suture of the whorls, as is
    also the case with the Ancillariæ and some Volutes." Bullia vittata,
    fig. 427, is an example of the genus. The name Subula is given by De
    Blainville to the other species of Terebra, so that if both these
    genera were admitted, the old genus Terebra must be expunged.

    BULLINULA. Beck. Species of BULLA, with produced conical spires, fig.
    253.

    BYSSOARCA. Sw. (_Byssus_ and _Arca_.) _Fam._ Arcacea, Lam. A genus of
    bivalve shells, composed of the Arca _Noæ_, and several other species,
    separated from the genus Arca on account of their shells being attached
    by means of a byssus passing through an hiatus in the ventral margins.
    B. _Noæ_, fig. 132. The species occur in Southern Europe, East and West
    Indies, China; also, on the coasts of Great Britain.

    BYSSOMYA. Cuvier. (_Byssus_ and _Mya_.) De Blainville states that
    although the shell of this proposed genus resembles Saxicava, the
    animal is sufficiently different to justify the separation.

    BYSSUS. ([Greek: Bussos], _byssus_, ancient name for linen.) The
    tendinous fibres by which some Bivalves are as it were anchored or
    moored to sub-marine substances. A fine example of this is to be seen
    in the Pinnæ which bear some resemblance to large Muscle Shells and
    have an hiatus in the margins of the valves through which a bunch of
    silken fibres passes. In the British Museum there is preserved a pair
    of gloves which have been woven of these fibres. The Byssus is peculiar
    to some bivalve shells such as Muscles, Hammer Oysters, Arca Noæ, &c.

    CALCAR. Montf. (a spur.) A genus composed of TROCHUS STELLARIS, Lam.
    and other depressed species of Trochus which are characterized by a
    stellated keel round the angle of the last whorl; but not including T.
    Imperialis, which is the genus Imperator, Montf. The difference
    consists in the latter being umbilicated and the former not. T.
    stellaris, fig. 358.

    CALCAREOUS, (_calx_, lime.) A term applied to a shell or to its
    operculum which is composed principally of lime or shelly matter, as is
    usually the case, in distinction from one which is of an horny,
    membranaceous texture. The greater number of shells are calcareous, but
    it forms an important point of distinction with regard to the
    operculum. The only difference between the genera Trochus and Turbo, as
    at present established, depends upon the calcareous or shelly, and the
    corneus or horny texture of the operculum.

    CALCEOLA. _Fam._ Rudistes, Lam. and Bl.--_Descr._ Equilateral,
    inequivalve, triangular; umbones separated by a large triangular disc
    in the lower valve; cardinal margin straight, linear, dentated; lower
    valve large, deep; upper valve flat, semi-orbicular, forming a kind of
    operculum to the lower.--_Obs._ This singular shell, known only in a
    fossil state, in the Palæozöic beds, is placed by Linnæus in the genus
    Anomia. Lamarck places it among his Rudistes, but Mr. Sowerby in his
    genera of Shells, states that it should be added to the family of
    Brachiopoda. Fig. 194, 195. C. Sandalina.

    CALLANTICA. Gray. POLLICIPES hispidus, Leach.

    CALLIA. Gray? A genus described as having a peculiarly polished shell
    like Pupina, but wanting the notch.

    CALLISOSTOMA. Sw. A genus of shells separated from TROCHUS, and thus
    described, "Imperforate; spire elevated, acute; aperture broader than
    high, transversely ovate, hardly sinuated at the base, and slightly
    oblique; shells always smooth, and often polished." C. zizyphina is
    mentioned as an example.

    CALLIRHOE. Montf. p. 362, vol. 2. Appears to be figured from the nut or
    inner portion of a large Belemnite.

    CALLISCAPHA. Gray? IRIDINA Nilotica, Sow. Zool. Journ. 1. pl. 2.
    Separated from Iridina on account of the hinge margin being smooth.

    CALLITHEA. Sw. A sub-genus of Mitræ, consisting of those species, which
    like M. sanguisuga, have the "spire and aperture of nearly equal
    length; internal channel nearly obsolete; shell with longitudinal
    linear ribs, crossed by transverse striæ and bands; base contracted."
    Swainson Mallac. Lard. Cyclop.

    CALLOSITY. A term used in general zoology to express those hard horny
    tumidities formed in the skin of some animals, (such as the Dromedary,
    for instance) in those parts which are most frequently used. It is not
    used in this sense by Conchologists, who apply it to those undefined
    tumidities or bumps which appear on the inner surface and hinge of some
    bivalve shells, and to the thickening over the umbilicus of Naticæ.
    Glycimeris, fig. 67. Natica, fig. 327, 328.

    CALPURNUS. Montf. OVULUM _verrucosum_, Auct. Distinguished by the small
    circular tubercle at the back of each extremity of the shell. Fig. 441.

    CALYPTRACEA. Lam. A family belonging to the first section of the order
    Gasteropoda, Lam., the shells of which are described as always
    external, covering the animal, and having no operculum. The genera
    contained in this family may be thus distinguished.

        1. CALYPTRÆA. Conical; apex central, septum spiral, cup-shaped, or
        forked; including _Infundibulum_. Fig. 234 to 238.

        2. CREPIDULA. Apex terminal; septum flat, reaching half across the
        aperture. Fig. 239.

        3. CAPULUS. Conical; apex obliquely curved, no septum. Fig. 240.

        4. EMARGINULA. Apex curved backwards; a notch in the anterior
        margin; including _Parmophorus_. Fig. 241, 242.

        5. CEMORIA. A slit _near_ the apex. Fig. 244.

        6. FISSURELLA. A slit _upon_ the apex. Fig. 245.

        7. RIMULA. A slit near the margin. Fig. 243.

        8. ANCYLUS. Apex curved sidewise. Fig. 246.

    CALYPTRACEA. Bl. The second family of the order Scutibranchiata. Bl.
    thus described: "Shell more or less conical, not spiral, or very
    slightly so; aperture large and entire." The genera included in this
    family are Crepidula, Calyptræa, Capulus, Hipponyx, and Notrêma.

    CALYPTRÆA. Lam. _Fam._ Calyptracea, Lam. and Bl.--_Descr._ Conical,
    patelliform, irregular, with an internal, lateral, salient plate or
    septum, varying in form.--_Obs._ The internal appendage is in some
    species cup-shaped, in some it juts out of the centre in a double
    point; in others it is only a small flap; and in others a spiral disc.
    These last, which are shaped like Trochus, are separated by De Montfort
    under the appellation INFUNDIBULUM; TROCHATELLA, Sw. The Calyptræa may
    be known from Crepidula by the septum, which in the latter is a flat
    plate reaching half way across the cavity. Fig. 234, 5, 6.

    CAMERINA. Brug. NUMMULITES, Auct.

    CAMILLUS. Montf. A genus founded upon a minute spiral shell, with a
    triangular aperture, turned over the back of the last whorl. It is
    figured in Soldani's Testacea Microscopica.

    CAMPULOTUS. Guettard. MAGILUS, Auct.

    CANAL. A groove which characterizes some spiral univalves, where the
    inner and outer lips unite at the front part of the aperture. This
    canal is drawn out in some shells to a considerable length, in others
    it is turned abruptly over the back. The family Canaliferæ, Lam. (fig.
    372 to 401), are all provided with this canal.

    CANALICULATED. Applied generally to any distinct groove or canal.

    CANALIFERA. (_Canalifères_, Lam.) A family belonging to the order
    Trachelipoda, Lam. nearly corresponding with the family Entomostomata
    in De Blainville's system, and described as having a canal of greater
    or less extent at the anterior part of the aperture. This canal is
    sometimes straight, sometimes tortuous, and in some genera it is
    recurved over the back of the shell. All the shells have an operculum,
    and the thickness of the perfectly formed outer lip does not increase
    with age. The Canalifera are characterized by having a canal, in
    distinction from the Purpurifera, which have only a notch. This family
    contains the following genera,

        1. CERITHIUM. Club-shaped. Fig. 372.

        2. POTAMIS. The same, fresh water. Fig. 377.

        3. NERINEA. The same, with internal folds. Fig. 374.

        4. TRIPHORA. Anterior and posterior canals closed so as to present
        three openings. Fig. 375, 376.

        5. TELESCOPIUM. Pyramidal, trochiform. Fig. 378.

        6. PLEUROTOMA. A slit on the upper part of the outer lip; including
        _Clavatula_. Fig. 379, 381.

        7. TURBINELLA. Three horizontal folds on the columella. Fig. 382,
        383.

        8. SPIRILLUS. Spire papillary; one fold on the columella. Fig. 384.

        9. CANCELLARIA. Three folds, and internal costæ. Fig. 385.

        10. FASCIOLARIA. Oblique folds, the lowest the largest. Fig. 386.

        11. FUSUS. Fusiform; no folds on the columella. Fig. 387.

        12. PYRULA. Pear-shaped. Fig. 388 to 390.

        13. STRUTHIOLARIA. Outer lip thickened; sinuated. Fig. 391.

        14. RANELLA. Two rows of varices; a canal at each extremity of the
        aperture. Fig. 393, 394.

        15. MUREX. Three or more rows of varices; only one distinct canal.
        Fig. 395, 396.

        16. TYPHIS. A tubular perforation between each varix. Fig. 397.

        17. TRITON. Varices not in rows. Fig. 398 to 401.

    CANCELLARIA. Auct. (From _Cancellatus_, cross-barred, like window
    frames or net work.) _Fam._ Canalifera, Lam. Entomostomata, Bl.--Descr.
    Oval, thick, cancellated; spire generally short, pointed; aperture
    sub-ovate, emarginated anteriorly, pointed at the posterior extremity;
    outer lip marked within by transverse ridges; inner lip spread over
    part of the body whorl, terminating in a straight, thick, obtuse
    columella, with several strong oblique folds. _Hab._ Indian Ocean,
    Coast of Africa, America, and West Indies. Fossils found in London Clay
    and Calc-grossier of Paris. Differing from Turbinellus in form and in
    the transversely ribbed inside of the outer lip. Fig. 315. C.
    reticulata.--_Obs._ The latest enumeration of the species of this genus
    is contained in a catalogue published by Mr. G. B. Sowerby, senior,
    accompanying the author's figures of the new species, amounting to 38,
    in parts 9 to 13 of the Conchological Illustrations. The greater part
    of these new species were brought to this country by Mr. Cuming.

    CANCELLATED. (From _Cancellatus_, cross-barred.) Applied generally to
    any shells which are marked by ridges crossing each other as
    Cancellaria, fig. 385.

    CANCILLA. Sw. A sub-genus of Mitræ, described as having "the whorls
    crossed by transverse linear ribs; inner canal wanting, plates very
    oblique; form slender; outer lip thin." _Ex._ M. Isabella, M. sulcata.

    CANCRIS. Montf. CREPIDULINA, Bl. A genus of microscopic Foraminifera.

    CANOPUS. Montf. A genus of microscopic Foraminifera.

    CANTHAPLEURA. Guild. A genus composed of those species of Chiton, which
    have the mantle rough, with moveable spines, prickles, or hairs. _Ex._
    C. spinosus, fig. 227.

    CANTHARIDUS. Montf. TROCHUS IRIS, Auct. and analogous species.
    Elenchus, Humph.

    CANTHARUS. Montf. A genus of microscopic Foraminifera.

    CANTHIDOMUS. Sw. A sub-genus of Melanopsis, thus described: "spire
    generally short; whorls coronated with spines, or marked with
    longitudinal ribs; base obtuse. C. costata, Sow. Gen. f. 3." Melanopsis
    costata, plates, fig. 315.

    CANTHORBIS. Sw. A sub-genus of the sub-family Trochinæ, Sw. Described
    as being "nearly disc-shaped: spire but slightly raised; the margin of
    the body-whorl flattened, and serrated with flat spines; inner lip
    united to the outer; pillar and aperture as in the last. (Tubicanthus.)
    C. imperialis. Mart. 173. f. 1714." This sub-genus appears to include
    those species of which De Montfort's genera Imperator and Calcar are
    formed.

    CANTHROPES. Montf. Described as resembling a Nautilus, with the whorls
    increasing so gradually, that the dorsal edge of the aperture advances
    but little beyond the last whorl. This genus is not mentioned by
    Blainville or Lamarck.

    CAPITULUM. Klein. POLLICIPES Mitellus, Lam. fig. 37*.

    CAPRELLA. ----? PLEKOCHEILUS, Guild. AURICULA Caprella, Lam.

    CAPRINA. D'Orb. DICERAS. Auct.?

    CAPRINUS. Montf. (Conch. Syst. t. 2. p. 143.) The figure appears to be
    intended to represent Helix Nux-denticulata.

    CAPSA. Brug. _Fam._ Nymphacea, Lam.--_Descr._ Equivalve transverse,
    subequilateral, subtrigonal; cardinal teeth, two in one valve, one
    notched in the other; lateral teeth remote, obsolete; an external
    ligament; two muscular impressions in each valve; a large sinus in the
    muscular impression of the mantle.--_Obs._ This genus is so nearly
    related to Donax, that it is difficult to distinguish it at first
    sight. The Capsæ, however, have not the short, plain, straight,
    posterior side, the distinct lateral teeth, nor the crenulated margins
    which characterize nearly all the Donaces. They are found in the
    British Channel, Brazil, and coast of Pacific Ocean. They are known
    from Erycina by not having the pit in the hinge for the ligament. Fig.
    109. C. Braziliensis.

    CAPULUS. Montf. _Fam._ Calyptracea, Lam.--_Descr._ Obliquely conical,
    posteriorly recurved; apex pointed, sub-spiral; aperture large,
    rounded, oval; with two muscular impressions, lateral, meeting behind;
    epidermis horny, rather velvetty. Britain, Mediterranean, West Indies,
    California, Australia.

    CARDIACEA. (Cardiacées, Lam.) A family of the order Conchifera
    Dimyaria, Lam. Most of the genera of shells contained in this family
    are included in the very extensive family of Conchacea, in the system
    of De Blainville. They are described as having irregularly formed
    cardinal teeth, generally accompanied by one or two elongated lateral
    teeth. Most of the species are ventricose, and have regular radiating
    ribs. This family contains the genera Cardium, Cardita, Cypricardia,
    Hiatella, Isocardia, and others enumerated in the explanation of
    figures 122 to 130. Their characters may be thus explained.

        1. CARDIUM. Two cardinal and two lateral teeth in each valve,
        including _Hemicardium_, _Papyridea_ and _Aphrodita_, in the last
        of which the teeth are nearly obsolete. Fig. 122, 123, 123*, 123**.

        2. VENERICARDIA. Two oblique cardinal teeth, one elongated;
        including _Cardita_, which has the umbones nearly terminal.
        _Pachymya_ may probably be included, but the hinge is not known.
        Fig. 121, 124, and 130.

        3. HIPPOPODIUM. One elongated cardinal tooth. Fig. 129.

        4. MEGALODON. Hinge broad, septiform, with a large tooth in the
        centre of one valve. Fig. 127.

        5. ISOCARDIA. Teeth laminar; umbones spiral. Fig. 126.

        6. CARDILIA. The same, with a septiform posterior laminar tooth.

        7. HIPPAGUS. Shaped like Isocardia, without teeth. Fig. 128.

    CARDILIA. Desh. _Fam._ Cardiacea, Lam. A genus formed for the reception
    of Isocardia semi-sulcata, Lam. and a small fossil shell, which
    Deshayes had formerly named Hemi-cyclonosta Michelini; thus described,
    (translation) "shell oval, oblong, longitudinal, white, heart-shaped,
    ventricose, with large prominent umbones; hinge with a small cardinal
    tooth and a pit at the side; a spoon-shaped projection for the
    reception of the internal ligament; anterior muscular impression
    rounded, not deep; the posterior being upon a thin, horizontal lamina,
    projecting in the anterior." Deshayes further remarks that although the
    animal is unknown, the relations of the genus may be established by
    means of the shell alone. Two families contain all the shells which
    have the internal ligament inserted in a spoon-shaped projection; in
    the one, that of the Anatinæ, the ligament is supported upon a little
    bone, which is not soldered to the hinge; in the other, that of the
    Mactraceæ, this little bone has no existence. In the former, all the
    shells are inequivalve; in the latter equivalve. And M. Deshayes,
    considering that the valves are equal, and that there is no separate
    bone to the hinge, is of opinion that the genus ought to be placed near
    the Lutrariæ, and not far from the Anatinæ. C. semisulcata, fig. 501,
    2.

    CARDINAL MARGIN. The edge of a bivalve shell on which the teeth is
    placed.

    CARDINAL TEETH. The teeth upon the hinge directly beneath the umbones
    of a bivalve shell, as distinguished from the lateral teeth, which are
    placed at a distance on each side. In Venus, fig. 119, the cardinal
    teeth, are marked by the letter c.

    CARDIOCARDITES. Bl. A genus separated from CARDITA, Auct. Thus
    described (translation) "oval species, with the inferior margin nearly
    straight, or a very little inflated, crenulated and completely closed.
    _Ex._ La C. Ajar, Adans Seneg. pl. 16. fig. 2."

    CARDISSA. _Sw._ A genus composed of those species of CARDIUM _Auct._
    which are heart-shaped. _Ex._ C. dionæum, fig. 122. And C. Cardissa.

    CARDITA. Brug. _Fam._ Cardiacea, _Lam._ Submytilacea, Bl.--_Descr._
    Equivalve, inequilateral, ovate, subquadrate or oblong, marked
    externally by ribs radiating from the umbones and terminating in a
    crenulated margin on the inner surface; cardinal teeth in one valve,
    one long, thick, oblique; another short, more straight; in the other
    valve one long, oblique, thick. Muscular impressions two in each valve,
    rather oval; palleal impression not sinuated.--_Obs._ This description
    includes Lamarck's genus Venericardia, which, although consisting of
    the more oblong species, is not considered sufficiently distinct to
    justify the separation. Cypricardia is distinguished from this genus by
    a remote lateral tooth. Mediterranean, Africa, East Indies, &c. Cardita
    calyculata, fig. 124.

    CARDIUM. Auct. _Fam._ Cardiacea, Lam. Conchacea, Bl.--_Descr._
    Equivalve, sub-equilateral, sometimes gaping posteriorly, ornamented on
    the outside by ribs radiating from the umbones; cardinal teeth, two in
    each valve, locked into each other crosswise, lateral teeth, two in
    each valve, remote; muscular impressions, two in each valve; palleal
    impression entire. Ligament external, inflated.--_Obs._ Although this
    genus includes many remarkable forms, the characters are so easily
    defined that there is no difficulty in distinguishing it from any other
    genus. C. angulatum, fig. 123. C. Groenlandicum, fig. 123*. APHRODITA,
    Lea. C. Hemicardium, fig. 123**. fig. 122. C. Dionæum. It is somewhat
    surprising that this genus, which contains some of the most beautiful
    forms of bivalve Testacea, should have been left till quite lately
    without any attempt to revise the species and settle the synonyms. The
    author of this Manual has endeavoured to remedy this defect by
    publishing a catalogue of all the species hitherto known, which amount
    to 97, including many new species described by him in the "Proceedings
    of the Zoological Society," in 1840. Parts 46 to 51, 149 and 150, and
    177 to 184 of his Conchological Illustrations contain figures of 60
    species. Cardia are frequent in all climates.

    CARINARIA. Auct. _Class_, Cephalopoda. _Division_, Monothalamia, Lam.
    _Fam._ Nectopoda, Bl.--_Descr._ Symmetrical or nearly so, conical,
    thin, glassy, fragile, patelliform; with a fimbriated dorsal keel; apex
    convolute, bent forwards; aperture oval, pointed at the dorsal
    extremity. _Hab._ Amboyna, Indian Ocean, and Mediterranean Sea.--_Obs._
    A most singular and beautiful shell, remarkable for its transparency,
    its fragile structure, and the dorsal keel, whence it derives its name.
    It was once so rare that a single specimen was known to realize one
    hundred guineas. Fig. 488. C. Mediterranea.

    CARINATED. (From _Carina_, a keel.) Applied to any shell having a
    raised, thin ledge, passing round a whorl or any other part of a shell,
    as in Carinaria, fig. 488.

    CARINEA. Sw. A genus formed for the reception of OVULUM gibbosum, Auct.
    and similar species, fig. 443.

    CARINELLA. Adanson. LUTRARIA papyracea, Lam. LIGULA, Leach. _Fam._
    Mactracea, Lam. Fig. 77.

    CARINIDEA. Sw. A sub-genus of the genus Canthorbis, Sw. (Turbo.) thus
    described, "Imperforate; spire pyramidal, acute; basal whorl concave
    beneath, and carinated round its circumference; aperture oval, entire,
    slightly angulated at the base of the pillar, which turns inwards. C.
    concavus, Martini, 168, fig. 1620, brevispinosus? Sow. Gen. (Turbo,)
    fig. 1."

    CAROCOLLA. Auct. _Fam._ Colimacea, Lam.--_Descr._ Orbicular, depressed,
    with the outer sides of the whorls angulated or keeled, whorls few;
    peritreme reflected; columella contiguous to the axis; epidermis
    thin.--_Obs._ This genus differing from Helix only in the whorls being
    angulated, is hardly distinct enough from the latter to justify the
    separation. In De Ferrusac's system these species constitute the
    division Helicigona, of the genus Helix. C. Lamarckii, fig. 277. East
    and West Indies, Philippines, South America and Europe.

    CARTILAGE. See LIGAMENT.

    CARYCHIUM. Müll. _Fam._ Auriculacea, Bl. Colimacea, Lam.--_Descr._
    Oblong or cylindrical, with gradually increasing whorls, few in number;
    aperture straight, short, with a fold on the columella.--_Obs._ This
    genus of minute land shells differs from Auricula chiefly in the soft
    parts. De Furrusac enumerates three species, C. Lineatum, C.
    Corticaria, (_Odostomia_, Flem.) and C. Minimum, fig. 301. De
    Blainville places it in his genus Auricula, as "species with two folds
    and a posterior tooth on the columella," giving a figure of A. Mysotis
    as his example, and quoting the name Phitia, Gray. Europe.

    CASSIDARIA. Lam. (From Cassis) _Fam._ Purpurifera, Lam. Entomostomata,
    Bl.--_Descr._ Oval, ventricose, spirally grooved and tuberculated, with
    a short turrited spire and a large aperture, terminating anteriorly in
    a recurved canal; outer lip thickened, reflected, undulated or
    denticulated; inner lip expanded over a part of the body whorl and the
    columella, with part of its lower edge free.--_Obs._ The recent species
    of this genus are not numerous; the few fossil species occur in the
    tertiary strata. C. carinata is found in Calc-grossier and London Clay.
    In general form this resembles CASSIS, but is at once distinguished by
    the canal, which does not turn abruptly back, but is slightly curved
    upwards. ONISCIA (C. Oniscus, &c. Lam.) is distinguished by the
    shortness of the canal, and the granulated surface of the inner lip.
    Fig. 407. C. Echinophora. Mediterranean.

    CASSIDEA. Sw. (from Cassis.) A genus composed of those species of the
    genus CASSIS, Auct. which have the "aperture wide; outer lip never
    broad or flattened, but sometimes slightly inflected; inner lip
    spreading, but never dilated or detached beyond the base into a
    prominent rim." East Indies. Ex. C. Glauca, fig. 411.

    CASSIDULA. Humph. PYRULA, Auct.

    CASSIDULINA. D'Orbigny. A genus of microscopic Foraminifera.

    CASSIS. (A helmet.) _Fam._ Purpurifera, Lam. Entomostomata,
    Bl.--_Descr._ Oval or triangular, ventricose, thick, generally
    tuberculated, with a short varicose spire; aperture long, sometimes
    narrow, with the outer lip thickened and reflected, generally
    denticulated; the inner lip spread over the surface of the body whorl,
    indented and incrassated at its inner edge; canal turned suddenly over
    the back of the shell. _Hab._ Seas of tropical climates. The fossil
    species are rare, occurring in the tertiary strata.--_Obs._ The large,
    common species of this well known genus are used for shell cameos and
    as ornaments on chimney pieces, grottos, &c. and are remarkable for the
    triangular disc, presented by the inner lip, which, in many species, is
    thickened and spread over the front of the body whorl and the angulated
    outer lip. The smaller, more rounded species, which have widened
    apertures, have been separated by Swainson, under the generic name
    CASSIDEA. The C. rufa, coarctata, &c. are formed by Mr. Stutchbury into
    a new genus under the name CYPRÆCASSIS, for reasons which will be
    stated under the word. Cassidaria is distinguished by the gradual curve
    of the canal. Fig. 410 is Cassis tuberosa, diminished.

    CASTALIA. Lam. _Fam._ Trigonées, Lam.--_Descr._ Fluviatile, equivalve,
    inequilateral, trigonal, with corroded umbones; hinge with two laminar,
    transversely striated teeth, one of which is posterior, remote from the
    umbones, short, divided, the other anterior, elongated; epidermis
    thick; internal surface pearly. Lamarck, in describing this shell,
    states, that he regards it as intermediate between Trigonia and Unio.
    It should, however, certainly have been placed in the family of
    "Nayades," and perhaps should form a part of the genus UNIO itself. C.
    ambigua, Lam. fig. 140. South America.

    CATILLUS. Brong. (A little dish.) INOCERAMUS, Sow.

    CATOPHRAGMUS. Sow. (From [Greek: Katô], _beneath_; [Greek: phragmos] _a
    place_ _paled in_.) _Order_, Sessile Cirripedes, Lam.--_Descr._ Light
    principal valves, cemented side by side in a circle; eight small
    pointed valves beneath, covering the joints of the upper circle, and
    numerous still smaller valves forming the base of the shell; operculum,
    four valves.--_Obs._ This is the only genus of Sessile Cirripedes,
    consisting of eight principal valves, excepting Octomeris, which is
    destitute of the accessary pieces from which the genus derives its
    name. Fig. 23. C. imbricatus. South Africa.

    CAUDAL CANAL. The elongated hollow process which terminates the
    aperture anteriorly of some univalve shells. For instance, Murex
    Haustellum, fig. 396, has an elongated caudal canal.

    CELLANTHUS. Montf. VORTICIALIS, Bl. A genus of microscopic
    Foraminifera.

    CELLULACEA. Bl. The second order of Cephalophora, Bl. consisting of
    doubtful microscopic bodies, with a number of variously arranged
    shells, as distinguished from the true Polythalamia, Bl. or chambered
    shells. See FORAMINIFERA.

    CEMORIA. Flemingii. Leach. A small patelliform shell, differing from
    Fissurella, in having the fissure placed behind the apex, which is
    produced, pointed and incurved. It is the Patella Fissurella, Müll.
    Patella Noachina, Chemn. F. Noachina, Sow. Puncturella, Lowe. Fig. 244.
    Cemoria Flemingii. Scotland and Tierra del Fuego.

    CENTRAL. A term used to indicate the position of the muscular
    impression of a bivalve shell when it is near the centre of the inner
    surface. It is also applied to the siphon perforating the septum of a
    chambered shell when it is placed near the centre of the plate.
    _Sub_-central is also used as a comparative term, to indicate the
    position of the siphon, or of the muscular impression, is _near_ the
    centre. Thus in Placuna (fig. 184), the muscular impression is central:
    in Exogyra (fig. 183), it is _sub_-central.

    CEPA. Humph. ANOMIA, Linn.

    CEPHALOPHORA. Bl. The first class of Malacozoæ, Bl. Divided into:
    _Order_ 1. Cryptodibranchiata; 2. Cellulacea; 3. Polythalamacea. The
    first consisting of Cuttle-fish, &c. which are destitute of shells; the
    second composed of those microscopic cellular bodies, which are
    regarded as shells by some authors; and the third containing the true
    chambered shells.

    CEPHALOPODA. Lam. (Cephalopodes.) ([Greek: Kephalê], _kephale_, head;
    [Greek: pous], [Greek: podos], _podos_, foot.) The fourth order of the
    _class_ Mollusca, Lam. containing molluscs, which are characterized by
    having a series of arms surrounding the head, which is placed above a
    sack-shaped body. This order is divided into Polythalamia, or
    many-chambered shells; Monothalamia, or single-chambered cephalopods;
    and Sepiaria, or cuttle-fish. Fig. 463 to 488.

    CEPOLIS. Montf. Belonging to the genus HELIX, Auct.

    CERATODES. Guild. ([Greek: Keratôdês], like a horn.) A genus composed
    of the flat, orbicular species of AMPULLARIA, Auct. which present so
    near a resemblance to the Planorbes, as to have been considered as
    belonging to them. Planorbis has, however, a horny texture, and no
    operculum, and it is always reversed, which may be observed by placing
    the spire upwards. Fig. 320, represents Ampullaria (Ceratodes)
    Cornu-arietis.

    CERIPHASIA. Sw. A sub-genus of Melanianæ, thus described, "Cerithiform;
    outer lip thin, dilated at the base; aperture small, slightly
    emarginate, without any internal groove; inner lip thin. C. sulcata,
    Sw. fig. 38. p. 204." (Sw. Lard. Cyclop. Malac. p. 342.)

    CERITHIUM. Brug. _Fam._ Canalifera, Lam. Entomostomata, Bl.--_Desc._
    Elongated, ribbed, tuberculated, or rarely smooth, with a lengthened,
    turrited, pointed, pyramidal spire, consisting of numerous whorls;
    aperture sub-quadrate, terminated anteriorly by a tortuous canal; outer
    lip thickened, sometimes reflected, expanded; inner lip thickened
    posteriorly; operculum horny, spiral, with numerous whorls.--_Obs._ The
    fresh-water shells described as Cerithia by Lamarck, are separated
    under the name Potamis, and may be known by the thick, horny epidermis.
    Triphora, Desh. has the canal closed, except at the extremities.
    Cerithium Telescopium, does not appear to present the same characters
    as the other Cerithia, and has been separated by some writers under the
    generic name Telescopium. Cerithium Aluco, fig. 372. Mediterranean,
    East and West Indies, Coasts of the Pacific, Gallapagos, Australia, &c.
    Some small species are British. Fossils are numerous in the tertiary
    beds.

    CERVICOBRANCHIATA. Bl. The second order of Paracephalophora
    Hermaphrodita, Bl. containing symmetrical patelliform shells, divided
    into the families Retifera and Branchifera.

    CETOCIS. Montf. _Fam._ Orthocerata, Lam. and Bl. Placed by De
    Blainville in his section of Belemnites, characterized as having small
    folds at the apex. _Ex._ B. Penicillatus.

    CETOPIRUS. Ranz. CORONULA BALÆNARIS, Auct. fig. 16.

    CHAMA. Auct. _Fam._ Chamacea, Lam. and Bl.--_Descr._ Inequivalve,
    irregular, thick, foliaceous, attached by the umbo of the lower and
    larger valve. External ligament placed in a groove, following the curve
    of the umbones. Umbones spiral, coiled round on the back of the valves;
    hinge with a thick, crenated, lengthened tooth, in one valve, entering
    a corresponding cavity in the hinge margin of the other; muscular
    impressions, two in each valve, distinct, lateral.--_Obs._ The Linnæan
    genus Chama, included the beautiful shells now called Tridacna. These
    are exceedingly different from the true Chama, being regular and
    unattached. The Chama (Tridacna) gigas, when at its full age and
    development, is the largest shell known. Specimens have occurred
    weighing upwards of 500 lbs., and measuring two feet across. Diceras
    may be known from Chama by the spiral horns into which the umbones are
    produced; Isocardia, by the regularity of the shells, and it is hardly
    necessary to mention Spondylus, which may be known by the triangular
    disc between the umbones; Cleidothærus, Stutch. which resembles Chama
    in general form, has a separate bony appendage attached to the hinge,
    and may, moreover, be distinguished by its elongated muscular
    impression. Fig. 153, C. Lazarus. E. and W. Indies.

    CHAMACEA. Bl. The seventh family of the order Lamellibranchiata, Bl.
    containing the genera Chama, Diceras, Etheria, Tridacna, Isocardia and
    Trigonia.

    CHAMACEA. Lam. A family belonging to the order Conchifera Dimyaria,
    Lam. described as inequivalve, attached, irregular; with or without a
    single rough tooth on the hinge; with two lateral muscular impressions
    in each valve. This family contains the genera--

        1. CHAMA. Leafy; umbones spiral. Fig. 153.

        2. ETHERIA. Very irregular, pearly, without teeth. Fig. 155.

        3. DICERAS. Like Chama, but the umbones free, produced. Fig. 154.

    CHAMBERED. When the cavity of a shell is not continuous, but is divided
    by shelly diaphragms or septa, it is said to be chambered. This is the
    case with the shells of the Polythalamous Cephalopoda, as in the
    Nautilus (see Introduction). The character is not confined to these, as
    it occurs in some species of Spondyli, and in several turrited
    univalves.

    CHAMOSTRÆA. De Roissy. CLEIDOTHÆRUS. Stutch.

    CHARYBS. Montf. A genus of microscopic Foraminifera.

    CHELIBS. Montf. A genus of microscopic Foraminifera.

    CHELINOTUS. Sw. A genus of "HALIOTIDÆ," Sw. including Velutina, Lam. a
    species of Sigaretus from Tonga, and Coriocella, Bl. Thus described,
    "Animal cheloniform, broad; depressed; the mantle larger than the
    shell, lobed in front; tentacula two, short, obtuse; eyes basal; mouth
    circular; shell ear-shaped, thin, fragile, imperforate; pillar none."

    CHELONOBIA. Leach. CORONULA Testudinaria, Auct. Fig. 15.

    CHERSINA. Humph. ACHATINA, Lam.

    CHICOREUS. Montf. A generic division of the genus MUREX, consisting of
    such species as have three ramified varices. _Ex._ M. inflatus, fig.
    395.

    CHILINA. Gray. _Fam._ Auriculacea, Bl. Colimacea, Lam.--_Descr._ Oval,
    thin, covered with an olive green epidermis; spire rather short,
    consisting of few whorls; aperture large, oval, rounded anteriorly;
    outer lip thin, joining the inner lip without a sinus; inner lip spread
    over part of the body whorl, terminating in a thick columella with one
    or two folds.--_Obs._ These shells differ from the true Auriculæ in the
    thinness of the outer lip. C. Dombeyana (Auricula Dombeyana, Auct.)
    Fig. 300. The illustrated catalogue published by the author (Sow.
    Conch. illustr. parts 135, 136) contains 13 species. Rivers of South
    America.

    CHILOTREMA. Leach. A sub-genus of HELIX, containing Helix lapicida,
    Auct. Gray, Turton, p. 140.

    CHIMOTREMA. ----? Belongs to HELIX.

    CHIONE. Megerle. CYTHERÆA maculosa, (fig. 117, c.) sulcata, circinata,
    &c. Auct. and other similar species.

    CHIRONA. Gray. A genus of Balanidæ, the shells consisting of six
    parietal valves and two opercular valves; the upper edges of the
    parietal valves are sloped and the structure is not tubular.

    CHISMOBRANCHIATA. Bl. The second order of the first section of
    Paracephalophora Monoica, Bl. Those Mollusca belonging to this order
    which have shells, have them either internal or external, but always
    scutiform, with depressed spires and wide, haliotoid, oblique
    apertures, without a columellar lip properly so called. This order
    partly answers to the family MACROSTOMATA, in the system of Lamarck. It
    contains the genera Coriocella, Sigaretus, Cryptostoma, Oxinoe,
    Stomatella and Velutina.

    CHITON. Auct. ([Greek: chiton], an integument.) _Fam._ Phyllidiana,
    Lam. _Class_, Polyplaniphora, Bl.--_Descr._ Oval, consisting of eight
    arched valves arranged in a series across the body of the animal and
    fixed in the skin which forms a rim around them, sometimes scaly,
    spinose, or rugose, sometimes smooth.--_Obs._ The genus Chiton,
    commonly called "Coat of Mail," from its resemblance to jointed armour,
    remains to the present day in exactly the same state with regard to its
    boundaries as that in which Linnæus found it, and in which he left it.
    That illustrious Naturalist placed it among the multivalves in his
    purely Conchological system, although the animal is totally different
    from the Cirripedes. The shells are prettily marked, and are found
    attached to the rocks in all seas of Tropical and Southern climates,
    but fossil species are almost unknown. Fig. 227, C. Spinosus. The genus
    is divided by Guilding into Chiton, Canthopleura, Phakellopleura,
    Chitonellus and Cryptoconchus. Zool. Journ. XVII. p. 27. The author of
    this manual has lately attempted a revision of this interesting but
    neglected genus, and has given a catalogue of all the species hitherto
    known, as far as they could be identified among the confused mass of
    synonyms and descriptions to be found in the works of various
    Conchological writers. This catalogue is to be found in his
    Conchological Illustrations, and refers to figures of 102 species, 92
    of which are contained in parts 38 to 45, and 159 to 176.

    CHITONELLUS. Lam. (From _Chiton_) Separated by Lamarck from Chiton, on
    account of the valves being placed at a greater distance from each
    other, the soft integument of the animal intervening. Fig. 228, C.
    striatus. Philippines.

    CHLOROSTOMA. Sw. A sub-genus of "Trochinæ." Sw. (Trochus) of which C.
    argyrostoma is given as an example. Sw. Lard. Cyclop. p. 350.

    CHONDRUS. Hartmann. ABIDA, Leach. A genus formed for the reception of
    PUPA secale, Drap. Pupa Juniperi, Montague, which have plaits in the
    aperture.

    CHRYSOAR. Montf. Probably a species of ORTHOCERAS.

    CHRYSODOMUS. Swains. "Distinguished from Fusus, by the comparative
    shortness of the basal channel, and the ventricose or enlarged shape of
    the body whorl. The beautiful orange-mouthed Whelk of England is a
    typical example; and the few others now known are all of a very large
    size, and chiefly found in Northern Seas, where they represent the more
    elegant Fusi of tropical latitudes; the outer lip is always thin and
    smooth." Sw. page 90, paragraph 78, described at page 308.

    CHRYSOLUS. Montf. POLYSTOMELLA, Bl. A genus of microscopic
    Foraminifera.

    CHRYSOSTOMA. Sw. A genus of the family "Rotellinæ," Sw. Thus described
    "Shell turbinate; the whorls few and convex; aperture effuse, round;
    inner lip thickened just over, and almost concealing the umbilicus.
    Nicobaricus, Martini, 182 fig. 1822-5." Sw. Lard. Cyclop. Malac. p.
    327.

    CHTHALAMUS. Ranz. _Fam._ Balanidea, Bl. Order, Sessile Cirripedes,
    Lam.--_Descr._ "Shell much depressed, valves thick, thickened at the
    base, with prominent areas; operculum nearly horizontal, composed of
    four valves."--_Obs._ This description would apply generically to the
    shell called Platylepas in the British Museum, only nothing is said
    about the prominent plates jutting from the internal surface of the
    valves. The difference between this genus and BALANUS consists
    principally in the horizontal position of the operculum, and general
    flatness of the shell. C. stellatus, fig. 18.

    CIBICIDES. Montf. A genus of microscopic Foraminifera.

    CIDARIS. Swains. A genus composed of TURBO Smaragdus, petholatus, and
    other similar species. The word Cidaris is, however, already in use for
    a genus of Echinæ.

    CIDAROLLUS. Montf. A genus of microscopic Foraminifera.

    CILIATED. (ciliæ, hairs.) Having minute hairs as in Orbicula, Lingula,
    &c. and the jointed feelers of the Cirripedes.

    CIMBER. Montf. NAVICELLA, Auct.

    CINERAS. Leach. (_Cinereus_, ash-coloured.) _Order_, Pedunculated
    Cirripedes, Lam.--_Descr._ Animal with a quadrilateral body, supported
    on a fleshy peduncle, with an opening in front of the upper part for
    the passage of a bunch of ciliated tentacula. Immediately above this
    aperture is a pair of small elongated valves, placed in a nearly
    horizontal position; at the lower part is another tripartite pair
    placed perpendicularly, one on each side, and a narrow, angulated,
    keel-shaped piece placed at the back.--_Obs._ The nearest approach to
    this genus is Otion. (C. Vittatus, fig. 42.) Found upon substances
    floating in the sea.

    CINEREOUS. (_Cinereus_) Ash-coloured.

    CINGULA. Fleming. RISSOA, Leach.

    CIONELLA. Jeffreys. _Fam._ Colimacea, Lam.--_Descr._ Oblong or
    elongated; last whorl large; apex rather acute; columella,
    sub-interrupted; aperture canaliculated, sub-effuse at the base;
    margins very unequal; no umbilicus. BULINUS octonus, lubricus, acicula,
    &c. Auct. C. lubrica, fig. 285.

    CIRCE. Schum. VENUS castrensis, fig. 117 d. V. sulcatina, arabica,
    pectinata, Auct. and other similar species.

    CIRRIPEDES. Lam. The tenth class of invertebrated animals, so named
    from the curled and ciliated branchia which protrude from the oval
    aperture of the shells. The class Cirripedes of Lamarck constitutes the
    entire genus _Lepas_ of Linnæus. They are divided into two sections;
    first, Sessile Cirr. attached by the basal portion of the shell;
    second, Pedunculated Cirr. supported upon a Peduncle. Figs. 14 to 45.

    CIRROBRANCHIATA. Bl. The first order of Paracephalophora Hermaphrodita,
    Bl. This order has been formed for the purpose of giving a place in the
    system to the genus Dentalium. The animal of which has lungs,
    consisting of numerous filaments, having their basal origin in two
    radical lobes under the neck.

    CIRRUS. J. Sowerby (cirrus, a tendril.) _Fam._ Turbinacea, Bl. and
    Lam.--_Descr._ Spiral, conical, with a hollow axis; whorls contiguous,
    numerous, rounded, or slightly angulated.--_Obs._ This fossil genus
    resembles Trochus, from which it is known by the deep funnel-shaped
    umbilicus. Fig. 349, C. nodosus.

    CISTULA. Humph. CYCLOSTOMA, Lam.

    CLANCULUS. Montf. TROCHUS _Pharaonis_, Lam.--_Obs._ This, with several
    other species, belong more properly to MONODONTA, Lam. ODONTIS, Sow.
    Fig. 361.

    CLATHODON. Conrad. GNATHODON, Gray.

    CLAUSILIA. Drap. (_Clausium_, a valve or folding door.) _Fam._
    Colimacea, Lam. Limacinea, Bl.--_Descr._ Spire elongated, consisting of
    many volutions; aperture small, sub quadrate, having several
    tooth-shaped folds on the columella. A small, elastic, shelly plate,
    attached to the columella within, called the Clausium, its office being
    to enclose the aperture when the animal has retired within the
    shell.--_Obs._ This last character distinguishes it from the Pupæ, to
    some of which it bears a very near resemblance. _Hab._ Land, in the
    central and southern parts of Europe, several British species. Fig.
    295, C. Macascarensis.

    CLAUSIUM. A name applied to the beautiful contrivance whence the genus
    Clausilia derives its name, consisting of a little bony tortuous plate,
    placed in a groove on the columella. Here it serves the purpose of a
    door, which, when not prevented by counteracting pressure, springs
    forward on its elastic ligament, and encloses the animal in his
    retirement. The aperture is opened by pushing back the clausium into
    the groove.

    CLAUSULUS. Montf. Conch. Syst. 1, 179. A genus of microscopic
    Foraminifera.

    CLAVA. Humph. CERITHIUM, Lam.

    CLAVAGELLA. Lam. (_Clava_, a club.) _Fam._ Tubicolæ, Lam. Pyloridea,
    Bl.--_Descr._ Two irregular flattish valves, one fixed or soldered, so
    as to form part of the side of an irregular shelly tube; the other free
    within the tube near the base.--_Obs._ The shells composing this genus
    are found in stones, madrepores, &c. and appear to form the connecting
    link between Aspergillum, which has both valves cemented into the tube;
    and Fistulana, in which both are free. Fig. 45, a fossil Clavagella.
    Found recent on the Coast of Malta and New South Wales.

    CLAVALITHES. Sw. A genus composed of some fossil shells, separated from
    the genus Fusus, which, having the general form of Turbinella Rapa, &c.
    are considered by Swainson, as holding an intermediate station between
    Fusus and the Turbinellidæ.--_Descr._ "Unequally sub-fusiform; the body
    whorl, and spire, being conic; and the canal suddenly contracted and
    attenuated; terminal whorls papillary; inner lip thick; pillar smooth,
    C. longævus, clavellatus, Noæ, ponderosus, Sw."--_Obs._ The papillary
    spire may form a sufficient reason for separating this genus from
    Fusus, while the absence of plates on the columella places them at a
    still greater distance from Turbinella.

    CLAVATE. When one extremity of the shell is attenuated, and the other
    becomes suddenly ventricose or globular, it is said to be Clavate.
    _Ex._ Murex Haustellum, fig. 396.

    CLAVATULA. Lam. The generic name by which Lamarck originally
    distinguished those species of Pleurotoma which were remarkable for the
    shortness of their canals. In his system, however, they are re-united
    to Pleurotoma. Fig. 381, P. Strombiformis.

    CLAVICANTHA. Sw. A genus separated from Pleurotoma, Lam. consisting of
    species, which are described as "thick, sub-fusiform; the surface
    rugose, and the whorls sub-coronated; channel short; slit assuming the
    form of a short, broad sinus. C. imperialis, E. M. 440, spirata, E. M.
    440, fig. 5, conica, E. M. 439, fig. 9, echinata, E. M. 439, fig. 8,
    Auriculifera, E. M. 439, fig. 10."

    CLAVICLE. (_clavis_, a key.) A little key. This term is applied to the
    bony appendage in the hinge of some species of Anatina, (those included
    in the generic term Lyonsia) Cleidothærus, Myochama, &c.

    CLAVULINA. D'Orb. A genus of microscopic Foraminifera.

    CLAVUS. Montf. A genus of microscopic Foraminifera.

    CLEIDOTHÆRUS. Hutch. ([Greek: Thairos], hinge, [Greek: Kleis],
    clavicle.) _Fam._ Chamaceæ or Myariæ, Lam.--_Descr._ Inequivalve,
    irregular, solid, attached; with one cardinal, conical tooth in the
    free valve, entering a corresponding indenture in the other; and an
    oblong shelly appendage, fixed by an internal cartilage in a groove
    under the umbones; muscular impressions, two in each valve, one
    elongated, the other uniform.--_Obs._ This shell is like Chama in
    general form, but is distinguished by the clavicle or shelly appendage
    from which its name is derived. Fig. 75. New South Wales.

    CLEODORA. _Per. et Les. Fam._ Pteropoda, Lam. Thecosomata,
    Bl.--_Descr._ Thin, transparent, pyramidal, with flat alate sides, and
    oval aperture. Fig. 221, C. cuspidata.

    CLISIPHONITES. Montf. Microscopic. LENTICULINA, Bl.

    CLITHON. Montf. NERITINA Corona, spinosa, &c. Auct. fig. 325.

    CLITIA. Leach. _Fam._ Balanidea, Bl. _Order_, Sessile Cirripedes,
    Lam.--_Descr._ Sub-conical, compressed, consisting of four unequal
    valves, two larger and two smaller, joined together side by side, by
    the interlocking of their dentated edges, a process somewhat like that
    which joiners call dove-tailing. Operculum, consisting of two unequal
    pointed valves.--_Obs._ Clitia is known from Creusia, by the
    articulations of the valves, and by the operculum, which in Creusia
    consists of four valves. Fig. 20. C. Verruca, (Lepas Verruca, Gmelin.)
    Britain and Peru.

    CLOSE. The margins of a bivalve shell are described as being close,
    when there is no hiatus between them in any part, otherwise they are
    described as _gaping_.

    CLOTHO. Faujas. _Fam._ Conchacea, Bl. More properly belonging to the
    Pyloridea, Bl.; and the Lithophagidæ, Lam.--_Descr._ "Oval, nearly
    regular, longitudinally striated, equivalve, sub-equilateral; hinge
    consisting of a bifid tooth, curved like a crochet, larger in one valve
    than in the other." This description is translated from Blainville, who
    states that he has never seen the shell. Annales du Museum D'Histoire
    Naturelle, tom. 9, pl. 17, fig. 4-6.

    CLYPEIFORM. (_Clypeus_, a shield.) Open, flat, shaped like a shield or
    buckler, as Umbrella, fig. 233, and Parmophorus, fig. 242.

    CLYPIDELLA. Sw. A sub-genus of Fissurella, described as having one
    extremity of the shell slightly raised. C. pustula. Sow. Gen. fig. 3.

    COAT OF MAIL. A common name given to shells of the genus Chiton, on
    account of their resemblance to jointed armour.

    COBRESIA. Hübner. VITRINA, Auct.

    COCHLIATE. (_Cochleare_, a spoon). Applied to any shell or part which
    is hollow and oval, as Patellæ, &c. The cavity containing the cartilage
    in Mya, fig. 71, is Cochleate.

    COCHLICELLA. One of the sub-genera into which De Ferrusac has divided
    the genus Helix, consisting of Bulinus decollatus, fig. 279, and
    similar species. See Helix.

    COCHLICOPA. Fer. A sub-genus of Helix, partly corresponding with
    Polyphemus of De Montfort, and consisting of species of Achatina, which
    have the outer lip undulated.

    COCHLITOMA. Fer. A sub-genus of Helix, corresponding with the genus
    Achatina, Auct. not including those with undulated outer lips.

    COCHLODINA. Fer. A sub-genus of Helix, including the genus Clausilia,
    Auct.

    COCHLODONTA. Fer. A sub-genus of Helix, containing Pupa Uva, Auct. &c.

    COCHLOGENA. Fer. A sub-genus of Helix, containing pupiform shells, such
    as Azeca tridens, fig. 290.

    COCHLOHYDRA. Fer. A sub-genus of Helix, composed of the genus Succinea,
    Auct.

    COCHLOSTYLA. Fer. A sub-genus of Helix, composed of the genus Bulinus,
    Auct.

    COLIMACEA. Lam. This Family, of the order Trachelipoda, Lam. includes
    all land shells, which might with propriety be divided into three
    sections, the first of which contain the following well-known genera:--

        1. SUCCINEA. Oval, transparent, oblique; animal amphibious. Fig.
        265, 266.

        2. HELIX. The type of which is the common snail shell. The
        separation of _Carocolla_, on account of the angulated whorls, or
        that of _Geotrochus_, on account of the turbinated shape, cannot be
        well maintained. Fig. 264, 267, 268, 273 to 276, 278 to 281, 294.

        3. ANOSTOMA. The aperture turned up towards the spire. Fig. 271,
        272.

        4. STREPTAXIS. Whorls excentric. Fig. 269, 270.

        5. BULINUS. Oval; aperture entire, including _Bulimulus_, _Balea_,
        _Cionella_, _Azeca_. Fig. 282 to 285, 289, 290, 296.

        6. ACHATINA. A notch terminating the columella. Fig. 286 to 288.

        7. PUPA. Cylindrical; including _Vertigo_, _Alæa_, &c. Fig. 291 to
        293.

        8. CLAUSILIA. Cylindrical, with a clausium. Fig. 295.

        _Obs._ The above are united in the system of De Ferrusac under the
        generic name Helix, and divided into sub-genera as explained under
        that word.

        The next section, included in the family Auriculacea, Bl., contains
        the genera Auricula, Chilina, Carychium, Marinula, Scarabæus, and
        Partula. Fig. 297 to 302.

        The third section contains the following genera of land shells with
        opercula.

        1. CYCLOSTOMA. Aperture round; operculum spiral. Fig. 303, 304.

        2. NEMATURA. Last whorl contracted; operculum spiral. Fig. 305.

        3. HELICINA. Aperture semi-lunar or angulated; operculum
        concentric. Fig. 306, 307.

        4. PUPINA. Shell polished; operculum concentric; aperture round.
        Fig. 524.

        5. STROPHOSTOMA. Aperture turned up towards the spire, like
        Anostoma, but said to have an operculum. Only known fossil. Fig.
        97.

    COLUMBELLA. Auct. (Columba, a dove.) _Fam._ Columellata, Lam.--_Descr._
    Thick, oval, or angular; with short spire, and long narrow aperture,
    contracted in the centre, and terminating in a short canal; outer lip
    thickened and dentated; inner lip irregularly crenated. Epidermis thin,
    brown. Operculum very small, horny.--_Obs._ Those species of Mitra,
    which resemble Columbella in shape, may easily be distinguished by the
    plaits on the columella. The Columbellæ are marine, and few fossil
    species are known. Fig. 430, C. Mercatoria. Swainson has divided this
    genus into the following: _Columbella_, consisting of C. Mercatoria,
    &c.; _Pusiostoma_, consisting of the Strombiform species;
    _Crassispira_, which is most probably a Cerithium; _Nitidella_,
    consisting of the smooth species; _Conidea_, consisting of the more
    conical species; another set of the more conical species has been
    removed from this family, and placed in that of the "Coninæ," but as
    they are separated by no essential character, we suppose this has
    merely been done for the purpose of completing the "circle" of the last
    mentioned family, which otherwise would not have reached the required
    number of five. Mediterranean, East and West Indies, South America,
    Coast of California, Gallapagos, &c.

    COLUMELLA. A solid column formed by the inner sides of the volutions of
    a spiral univalve. It is sometimes described as the inner lip of the
    aperture, of which it forms a part; but the term would be more properly
    confined to that portion of the inner lip which is seen below the body
    whorl, over which the remainder of the lip is frequently spread. All
    the inner edge of the aperture, including that part of it which covers
    the body whorl, is called the columellar lip. In fig. 431, the anterior
    termination of the columella is indicated by the letter c. The axis, is
    an imaginary line drawn strictly through the centre of the whorls,
    whether their inner edges form a solid column or not.

    COLUMELLAR LIP. The inner lip. See COLUMELLA.

    COLUMELLATA. Lam. A family of the order Trachelipoda, Lam. containing
    the following genera:--

        1. MITRA. Elongated; aperture narrow; strong folds on the
        columella; including _Mitrella_, _Mitreola_, _Tiara_, and
        _Conohelix_. Fig. 431, 432.

        2. MARGINELLA. Outer lip reflected; including _Volutella_,
        _Persicula_, _Gibberula_, and _Glabella_. Fig. 437.

        3. COLUMBELLA. Outer and inner lips denticulated or granulated.
        Fig. 430.

        4. VOLUTA. Outer lip thickened; folds on the columella; aperture
        generally wide; apex papillary; including _Scaphella_, _Harpula_,
        _Volutilithes_, _Cymbiola_. Fig. 433, 436.

        5. MELO. Shell comparatively light; spire short, sometimes hidden;
        apex round, spiral; folds on the columella laminar. Fig. 435.

        6. CYMBA. Upper edge of the aperture separated from the body whorl
        by a flat disc; apex mammillated, irregular; folds on the
        columella. Fig. 434.

        7. VOLVARIA. Cylindrical; aperture long, narrow; folds on the
        columella; spire hidden. Fig. 439.

    COLUS. Humphrey. FUSUS, Lam.

    COMPLANARIA. Sw. A subgenus of ALASMODON (Unio), thus described, "shell
    winged; the valves connate; the bosses very small and depressed;
    cardinal teeth two or three; lateral teeth represented by irregular
    grooves. C. gigas (Unio), Sow. Man. fig. 141. Alasmodon complanatus,
    Say. C. rugosa, Sw."

    COMPRESSED. Pressed together, or flattened. The application is the same
    as in common use. A Patella may be described as a vertically compressed
    cone. A Ranella, on account of the two rows of varices skirting the
    whorls, appears, as it were, laterally compressed. A bivalve shell is
    said to be compressed when it is flat, that is, when but a small cavity
    is left in the deepest part when the valves are closed. Perhaps the
    Placuna placenta, fig. 184, is the most remarkable instance of this.

    CONCAMERATIONS. (_Con_, with, _camera_, a chamber.) A series of
    Chambers joining each other, as in Nautilus, Spirula, &c.

    CONCENTRIC. A term applied to the direction taken by the lines of
    growth in spiral and other shells, (_longitudinal_ of some authors.)
    Every fresh layer of shelly matter forms a new circle round an
    imaginary line, drawn through the centre of the spiral cone, down from
    the nucleus. When the edges of the successive layers are marked by any
    external characters, the shell is said to be concentrically striated,
    banded, grooved, costated, &c. A fine illustration of the latter is to
    be seen in the Scalaria or Wentletrap, fig. 351, Lines, bands, ribs,
    &c. in the opposite direction, (_transverse_ of some authors,) are
    "radiating" in bivalves, as the ribs of Cardium, fig. 123, and "spiral"
    in univalves, that is, following the direction of the whorls, as the
    bands of colour in Pyramidella, fig. 342.

    CONCHACEA. Bl. The eighth family of the order Lamellibranchiata, Bl.
    The shells are described as follows: nearly always regular, valves
    closed all round; apices curved towards the anterior; dorsal hinge
    complete, with teeth and ligament; the latter external or internal,
    short and thick; two distinct muscular impressions, united at the lower
    part by a parallel impression, which is frequently sinuated at the
    posterior. The genera described in this family are divided into three
    sections. First, those which are regular, and have distant lateral
    teeth, Cardium, Donax, Tellina, Lucina, Cyclas, Cyprina, Mactra, and
    Erycina. Second, those which are regular, and have no distant lateral
    teeth, Crassatella and Venus. Third, those which are irregular,
    Venerupis, Coralliophaga, Clotho, Corbula, Sphænia, and Ungulina.

    CONCHACEA. Lam. A family of Lamarck's order Conchifera Dimyaria.
    Regular, unattached in general, closed at the sides. They are always
    more or less inequilateral. The _Marine_ Conchacea are those which
    inhabit the sea. The fluviatile Conchacea are those which are found in
    rivers, ponds, &c. Each of these contain various genera, which may be
    arranged as follows:--

    _Fluviatile._

        1. CYRENELLA. Three cardinal teeth; ligament long; shell thin. Fig.
        114.

        2. CYCLAS. Thin, oval; cardinal and lateral teeth; anterior side
        shortest, including _Pera_.

        3. PISIDIUM. The same, with the posterior side shortest. Fig. 112.

        4. CYRENA. Thick; cardinal and lateral teeth. Fig. 113.

        5. POTAMOPHILA. Two thick cardinal teeth. Fig 115.

    _Marine._

        1. CYPRINA. Two cardinal teeth, and one remote lateral tooth. Fig.
        116.

        2. VENUS. Three cardinal, no lateral teeth; including _Artemis_.
        Fig. 118, 119, 119a.

        3. CYTHEREA. Several cardinal teeth; one very short lateral tooth.
        Fig. 117, 117_a_, 117_b_, 117_c_, 117d.

        4. PULLASTRA. Cardinal teeth notched, otherwise like Venus. Fig.
        120.

        5. ASTARTE. Three cardinal teeth; ligament short. Fig. 110.

           VENERICARDIA belongs to the Cardiacea.

    CONCHIFERA. Lam. The 11th class of Invertebrata, consisting of all
    those animals which have bivalve shells. Lamarck divides the class into
    Dimyaria, which have two adductor muscles; and Monomyaria, which have
    but one.

    CONCHOLEPAS. Montf. (CONCHA, a shell; lepas, a stone or rock.) _Fam._
    Purpurifera, Lam. Entomostomata, Bl.--_Descr._ Oval, imbricated, thick;
    with a very short spire and large oval patelliform aperture,
    terminating anteriorly in a slight emargination; outer lip crenated,
    with two produced points or teeth towards the anterior, inner lip
    smooth, nearly flat, reflected over the last whorl, so as nearly or
    entirely to cover it; operculum horny. Marine, only one species known,
    from Peru.--_Obs._ This shell is placed near Patella by Lamarck, on
    account of its large open aperture; but having a horny operculum, and
    resembling Purpurea in other respects. Fig. 418. Concholepas Peruviana.

    CONCHOTRYA. Gray. (_Concha_, a shell; [Greek: Truo], (_tryo_) to bore.)
    _Order_, Pedunculated Cirripedes, Lam.--_Descr._ Five pieces, two pairs
    ventral, one single; shaped like Pentelasmis. Found in holes.

    CONCHYLIOMORPHITE. A term used by De Blainville to designate the cast
    or model of a fossil shell, formed by a siliceous substance which has
    entered or surrounded it when in a liquid state, and subsequently
    become hardened into flint. The shell has afterwards decomposed or
    fallen off by accident, leaving its external or internal characters to
    be conjectured from the monumental impressions that remain.

    CONCHYTA. Hupsch Mus. CALCEOLA, Lam.

    CONE. A common name for shells of the genus Conus.

    CONE. This mathematical term is used by conchologists in its utmost
    latitude of signification to express a body, which in its formation,
    commences in a small point, called the apex, and increases in width
    towards the conclusion or base. It is applied to all shells, whether
    the increase in width be gradual or sudden; or whether in its growth,
    it takes a straight, oblique, curved, or spirally-twisted course. In
    this sense, a bivalve would be described as a pair of rapidly
    enlarging, oblique cones, and the aperture of every spiral shell would
    be its base. But this phraseology being in disuse, it is only mentioned
    here that it may be understood when occasionally met with.

    CONELLA. Sw. A genus composed of species of the genus Columbella, Lam.
    which have a conical form, and which, on that account, are considered
    by Swainson as belonging to his family of Coninæ. Swains. Lardner.
    Cyclop. Malac. described at p. 312. C. picata, Sw. fig. 17, a. p. 151.

    CONFLUENT. A term applied to two parts of a shell when they gradually
    flow into each other, as, for instance, the inner and outer lips of
    Univalves when they pass into each other at the anterior extremity,
    without the intervention of a notch or angle.

    CONIA. Leach. _Fam._ Balanidea. _Order_, Sessile Cirripedes,
    Lam.--_Descr._ Four rather irregular valves, of porous structure,
    placed side by side, so as to form a circular cone, supported at the
    base on a shelly plate, and closed at the aperture by an operculum
    consisting of four valves in pairs. Distinguished from Creusia by its
    porous structure and by its flat support; that of Creusia being
    cup-shaped. Fig. 21, Conia porosa.

    CONICAL. A term applied in the ordinary sense, and not as explained
    above, under the word CONE.

    CONIDEA. Sw. A genus separated from Columbella, Lam. thus described,
    "Mitra shaped, fusiform; spire equal or longer than the aperture; the
    whorls tumid; outer lip slightly gibbous above, contracted below;
    margin not inflected; striated within; inner lip terminating in an
    elevated ridge, but with the teeth obsolete. C. semipunctata,
    (_Columbella_, Lam.) Mart. 44. fig. 465, 466." Africa.

    CONILITES. _Fam._ Orthocerata, Lam. & Bl.--_Descr._ "Conical, straight
    or slightly curved; having a thin external covering, independent of the
    nut or alveole, which it contains. Alveole transversely chambered,
    sub-separable." (Translated from Lam.)--_Obs._ The difference between
    Belemnites and Conilites is that the external sheath of the latter is
    thin, and not filled up with solid matter, from the point of the
    alveole to the apex, as in the former. De Blainville places in this
    genus the genera Thalamulus, Achelois and Antimomus, Montf. two of
    which are figured, Knor. Sup. Fab. iv. fig. 1. 1. 8. 9. Conilites
    Pyramidatus, fig. 470.

    CONILITHES. Sw. A sub-genus of Coronaxis, Sw. (Coni, with coronated
    whorls) thus described, "Conic; spire considerably elevated; the
    aperture linear, C. antediluvianus, Sow. Gen. f. 1."

    CONOHELIX. Sw. (_Conus and Helix._) The generic name given to those
    species of Mitra which are conical in form. Fig. 432, C. marmorata.

    CONOPLÆA. Say. _Order_, Sessile Cirripedes, Lam. A genus composed of
    Balani, attached to the stems of Gorgonia, having their bases
    elongated. _Ex._ fig. 27, Balanus Galeatus.

    CONORBIS. Sw. A genus composed of species of CONUS, such as C.
    dormitor, (Sowerby, gen. fig. 8) which have elevated spires and the
    upper part of the outer lip deeply sinuated. Mr. Swainson considers
    these fossil species as analogous to the Pleurotomæ. _Sw._ Lard.
    Cyclop. Malac. p. 312.

    CONOVULUM. A genus proposed by Lamarck, to include the small, conical
    species of Auricula, which have the outer lip simple. This genus was
    afterwards abandoned by the author. _Ex._ fig. 298, Auricula
    coniformis.

    CONTIGUOUS. (_Contingo_, to touch.) A term applied to the whorls of
    spiral shells when they rest upon, or touch each other. This is the
    case in a great majority of instances. When, on the contrary, there is
    a space between the whorls, they are said to be non-contiguous,
    detached, or free. Examples of non-contiguous whorls are to be seen in
    Scalaria, fig. 351 (in this case, the distance between the whorls is
    small), and in Crioceratites, fig. 482. A "_Columella contiguous to the
    axis_," is when in the centre of the shell and takes the place of the
    imaginary line which forms its axis.

    CONTINUOUS. Carried on without interruption, as the siphon in Spirula,
    the varices in Ranella, fig. 394, which, occurring in a corresponding
    part of each whorl, form a continuous ridge.

    CONULARIA. Miller. A genus of Orthocerata, described as conical,
    straight, or nearly so, divided into chambers by imperforate septa;
    aperture half closed; apex solid, obtuse; external surface finely
    striated. Resembling Orthoceras, but wanting the siphon. Fig. 449.

    CONUS. Auct. ([Greek: Kônos], a cone.) _Fam._ Enroulées, Lam.
    Angyostomata, Bl.--_Descr._ Conical, convolute, with a short spire,
    consisting of numerous whorls; and narrow lengthened aperture,
    terminating in a slight emargination at each extremity; outer lip thin;
    epidermis thin; operculum small, pointed, horny.--_Obs._ This
    well-known genus of shells is easily distinguished from any other, by
    its conical form, its smooth columella, its narrow aperture, and thin
    outer lip. The form of the spire varies from flat and even partially
    concave, to a regular pyramidal cone; and the upper edges of the whorls
    are rounded in some species, angulated in others, and in some are waved
    or coronated. The variety of marking and the numerous delicate tints of
    these shells have caused them to be highly appreciated by amateur
    collectors; and many species, as the C. Ammiralis, or admiral; the C.
    Gloria Maris, or Glory of the Sea; the C. Cedonulli ("I yield to
    none"), and others, have always produced good prices in the markets. We
    give figures of the principal forms, as expressed in the genera
    proposed by De Montfort, of Rhombus, Hermes, Rollus and Cylinder, in
    figures 459 to 462. Many new species were brought to this country by
    Mr. Cuming, and are represented in parts 24, 25, 28, 29; 32, 33, 36,
    37; 54, 55, 56, 57; 147, 148; 151 to 158 of the Conchological
    Illustrations, by G. B. Sowerby, jun. See CORONAXIS, Swainson. The
    cones are mostly tropical, some are found as far north as the
    Mediterranean, and south as the Cape of Good Hope. The most beautiful
    species are from the East and West Indies.

    CONVOLUTÆ. (Enroulées, Lam.) A family of the 2nd section of the order
    Trachelipoda, Lam. the genera of which may be distinguished as
    follows:--

        1. CYPRÆA. Lips thickened, inflected, with teeth; spire hidden,
        including _Cypræovulum_, _Luponia_, _Trivia_. Fig. 444 to 450.

        2. OVULUM. Lips thickened, inflected, with slight crenulations;
        spire hidden. Fig. 440 to 443.

        3. ERATO. Lips thickened, inflected; spire visible; a groove down
        the back. Fig. 454.

        4. TEREBELLUM. Cylindrical, open at the anterior extremity;
        columella smooth; suture of the spire canaliculated. Fig. 451, 452.

        5. OLIVA. Columella plaited, swelled into a varix at the anterior.
        Fig. 457, 458.

        6. ANCILLARIA. The same, but the suture of the spire covered with
        enamel. Fig. 455, 456.

        7. CONUS. Turbinated, numerous whorls; spire flat or short,
        conical; columella smooth. Fig 459 to 462.

    CONVOLUTE. (_Con_, together; _volvo_, to revolve). This term can be
    strictly applied only to symmetrical shells, signifying that the
    volutions are parallel to each other in a horizontal direction, as in
    the Ammonites, &c.; but the term is also commonly used in describing
    such shells as Conus, in which, the direction of the whorls being
    scarcely oblique, the last whorl almost entirely covers those which
    precede it. This is the case with Lamarck's family of Enroulées. Fig.
    440 to 462.

    CORALLIOPHAGA. Bl. CYPRICARDIA Coralliophaga, Lam.--_Descr._ Oval,
    elongated, finely striated from the apex to the base, cylindrical,
    equivalve, very inequilateral; umbones slightly raised and quite
    anterior; hinge nearly the same in both valves; two small cardinal
    teeth, one of which is bifid, placed before a kind of lammellated
    tooth, beneath a very slender external ligament; two small, distant,
    muscular impressions, united by a striated palleal impression, which is
    strongly striated posteriorly.--_Obs._ This shell, which is found in
    the empty holes of dead Lithodomi, in some instances conforming its
    shape to its situation, differs from Cypricardia of Lamarck,
    principally in its cylindrical form. C. Carditoidea, fig. 92.
    Mediterranean and East Indies.

    CORBICULA. Megerle. CYRENA, Lam.

    CORBIS. Cuv. (_A basket._) _Fam._ Nymphacea, Lam.--_Descr._ Transverse,
    oval, thick, ventricose, equivalve, sub-equilateral, free, cancellated,
    with denticulated internal margins; hinge with two cardinal and two
    lateral teeth in each valve; of the latter, one near and one remote
    from the umbones; muscular impressions lunulate, two in each valve,
    united by an entire palleal impression, without a sinus.--_Obs._ This
    genus, of which only two or three recent species are known, resembles
    many species of Venus and Cytherea in general form; but differs in
    having lateral teeth, and in the palleal impressions which in all the
    Veneres, &c. is sinuated. From Lucina it may be known, not only by its
    oval form, but also by the muscular impressions, which, in Lucina are
    produced into an elongated point; it will also be distinguished from
    Tellina, by the want of a posterior fold in the valve, for which that
    genus is remarkable. C. Fimbriata, fig. 101, is an inhabitant of the
    Indian Ocean. Several fossil species are found in the recent
    formations, above the chalk, at Grignon and Hauteville.

    CORBULA. Brug. (_A little basket._) _Fam._ Corbulacea, Lam. Conchacea,
    Bl.--_Descr._ Inequivalve, sub-equilateral, transverse, gibbose, not
    gaping; cardinal tooth in each valve, conical, curved, prominent,
    inserting its extremity into a pit in the opposite hinge; cartilage
    attached to the tooth of the smaller valve, and the pit in the larger;
    muscular impressions, two in each valve, distant, rather irregular;
    palleal impression posteriorly angulated.--_Obs._ The shells composing
    this genus were placed in Mya by Linnæus, but differ from the true Myæ
    in having a sinus in the palleal impression, and a prominent
    ligamentiferous tooth in each valve, whereas the Myæ have but one. The
    Corbulæ are marine, some species inhabiting the British coasts. Fossil
    species occur abundantly in green sand, London clay, crag, and
    corresponding formations. Fig. 89. C. Nucleus.

    CORBULACEA. (Corbulées, Lam.) A family of the order Conchifera
    Dimyaria, Lam., containing the genera--

        1. CORBULA, with a prominent curved tooth. The Fresh-water species
        has been separated under the name _Potamomya_. Fig. 89.

        2. PANDORA. Thin, pearly, no teeth. Fig. 90.

    CORDIFORM. (_Cor_, a heart.) Heart-shaped, a term applied generally to
    any shell which may be fancied to resemble a heart in shape, as
    Isocardia, fig. 126, and Cardium Dionæum, fig. 122.

    CORIACEOUS. (_Corium_, leather.) Of the substance of leather. _Ex._,
    the integument into which the valves of Chitones are inserted.

    CORIOCELLA. Bl. The animal designated by this name is described by De
    Blainville as being without any traces of shell, either internal or
    external. This must have arisen from the imperfection of the specimen
    described, probably deprived by accident of its shell. The testaceous
    appendage of the Coriocella is now well known to naturalists. It is a
    milky white, transparent shell, shaped like Sigaretus.

    CORNEA, and PISUM, Megerle. CYCLAS, Lam.

    CORNEO-CALCAREOUS. A term used to express the mixture of horny and
    shelly matter which enters into the composition of some shells,
    Aplysia, for instance. It is also applied to those Opercula, which are
    horny on one side, and testaceous on the other, as that of Turbo.

    CORNEUS. Horny. A species of Patella has had the specific name corneus
    given to it, because its texture more nearly resembles that of a horn
    than that of a shell. The epidermis of fresh-water shells is of a
    similar composition.

    CORNUCOPIA. Humph. LEPAS, Linn.

    CORONALES. See CORONULAR MULTIVALVES.

    CORONATED. (_Corona_, a crown.) Applied to shells when ornamented with
    a series of points, tubercles, &c., round the upper edges of the
    volutions. _Ex._ Conus Nocturnus, fig. 459.

    CORONAXIS. One of the two genera into which Swainson divides the genus
    Conus, consisting of those species which have a row of tubercles on the
    upper edge of the whorls, an arrangement by which he would in many
    instances, not only separate between two individuals of the same
    species, but also between two parts of the same shell; for instances
    occur in which the earlier whorls are coronated, while the body whorl
    and the penultimate are perfectly plain.

    CORONULA. (_Corona_, a crown, dim.) _Order_, Sessile Cirripedes, Lam.
    _Fam._ Balanidea, Bl.--_Descr._ Six radiated valves, joined side by
    side in a circle, forming a depressed cone; internal structure of the
    valves, porous or chambered; thickened at the base; operculum
    consisting of four valves in pairs; imbedded horizontally in a
    cartilaginous substance.--_Obs._ The shells composing this genus are
    found partly imbedded in the skin of whales, and the shells of
    tortoises, and are therefore destitute of the shelly foundation on
    which the Balani and other Coronular Multivalves are supported. C.
    Testudinaria, (CHELONOBIA, Leach,) fig. 15. C. Balænarum, (CETOPIRUS,
    Ranz.) fig. 16. C. Diadema, (DIADEMA, Ranz.) fig. 17.

    CORONULAR MULTIVALVES are those which have their parietal valves joined
    together side by side in a circle, surrounding the body of the animal,
    so as to form a sort of coronet. This is the characteristic of the
    Sessile Cirripedes of Lamarck's system, the Balanidea of De Blainville.

    CORRODED. (_Corrodo_, eat away, consume.) The umbones, apices, and
    other thick parts of shells, are frequently worn away or consumed by
    the action of the element in which they exist. As the thickest parts of
    some shells are the most subject to this operation, it appears to the
    author to arise from the outer surface of the shell, being less under
    the influence of the animal juices than the other parts; and therefore,
    more exposed to the influence of the surrounding element. This,
    however, is not the case with respect to the Nayades and other
    fresh-water shells; with these, corrosion does not take place until
    after the thick epidermis which covers them, becomes wounded by some
    means or other, and then the animal thickens its shell within as fast
    as it is corroded without.

    CORTALUS. Montf. (Conch. Syst. 1. 115.) A genus of microscopic
    Foraminifera, placed by De Blainville in a division of the genus
    Rotalites.

    COSTATED. Ribbed, as Cardium Angulatum, fig. 123.

    COSTELLARIA. A sub-genus of the genus Tiara, Sw. (Mitra.) C. rigida.
    Swainson, Zool. Ill. 1st series, pl. 29.

    COWRY. A common name for shells of the genus Cypræa.

    CRANIA. (_Cranium_, a skull.) _Fam._ Rudistes, Lam. _Order_,
    Pallio-branchiata, Bl.--_Descr._ Inequivalve, equilateral, irregular,
    sub-quadrate; upper valve patelliform, conical, with the umbo near the
    centre; lower valve attached by its outer surface; muscular
    impressions, 4 in each valve; two large, posterior, distant; two small,
    near to each other, central. No hinge teeth; no ligament.--_Obs._ This
    genus properly belongs to the Brachiopoda, Lam. It differs from
    Orbicula in the mode of attachment, which in the latter, is by a byssus
    passing through the lower valve, and not by the valve itself. Hipponyx
    has only two muscular impressions in each valve. The name of this genus
    is derived from the inner surface of the attached valve, which presents
    a remarkable resemblance to the facial portion of a human skull. This
    appearance is caused by the situation and elevated edges of the
    muscular impressions. Fig. 197. Coasts of Britain and Mediterranean.

    CRASSATED. (_Crassus_, thick.) Used to express a thickness in the
    substance of a shell. _Ex._ Glycimeris, fig. 67.

    CRASSATELLA. Lam. (_Crassus_, thick.) _Fam._ Mactracea, Lam. Conchacea,
    Bl.--_Descr._ Equivalve, inequilateral, close, thick, rounded
    anteriorly, rostrated posteriorly, with denticulated margins, smooth,
    or ribbed transversely; hinge with a triangular pit containing the
    cartilage, two anterior cardinal teeth, and a posterior depression in
    one valve; one anterior tooth and a slight anterior marginal elevation,
    and a posterior elevation in the other valve. Muscular impressions
    distant, strongly marked. Palleal impression not sinuated.--_Obs._ The
    few recent species known are marine, several being brought from the
    coasts of New Holland. Fossil species are found in Calcaire-grossier
    and London clay. The Crassatella are known from the Veneres, &c., by
    the ligamentary pit in the hinge, and from Lutraria and Mactra by the
    thickness and closeness of the shell. Fig. 84, C. rostrata.

    CRASSINA. Lam. ASTARTE, Sow.

    CRASSIPEDES. Lam. (_Crassus_, thick; _pes_, foot.) The first section of
    the order Conchifera Dimyaria, Lam. In this section the foot of the
    animal is thick, and the shell gapes considerably. It is divided into
    the families Tubicolæ, Pholadidæ, Solenidæ, and Myaria. Fig. 44 to 76.

    CRASSISPIRA. Sw. A genus separated from COLUMBELLA, Auct. for which Mr.
    Swainson quotes "Pleurotoma Bottæ, Auct." Crassispira fasciata, Sw.
    Lardn. Cyclop. Malac. p. 313.

    CRENATED. (_Crena_, a notch.) Applied to small notches, not
    sufficiently raised or defined, to be compared to teeth. _Ex._ The
    hinge of Iridina, fig. 150.

    CRENATULA. Lam. _Fam._ Malleacea, Lam. Margaritacea, Bl.--_Descr._
    Compressed, foliated, irregular, sub-equivalve, inequilateral, oblique;
    umbones terminal; hinge linear, nearly straight, with a series of
    excavations, containing the cartilage, while the intervening ridges are
    covered with the ligament, properly so called. Muscular impression
    oblong, indistinct.--_Obs._ This genus is known from Perna by the
    hinge, which in the latter is composed of a series of regular,
    straight, ligamentary grooves placed across it. In Crenatula also there
    is no passage for the byssus, as in Perna. C. Mytiloides, fig. 168.
    Coasts of the Red Sea.

    CRENULATED. Finely crenated or notched.

    CREPIDULA. Lam. (_Crepidula_, a little slipper.) _Fam._ Calyptracea,
    Lam. and Bl.--_Descr._ Oval, irregular, patelliform; apex lateral,
    incurved, or sub-spiral; external surface convex, smooth, ribbed,
    waved, or covered with spines; interior concave, smooth, with a
    flattish septum reaching nearly half across the cavity; epidermis light
    brown.--_Obs._ The difference between this genus and Calyptræa is that
    in the latter, the septum is more free from the sides of the shell, so
    that, instead of forming a regular plate, covering half the aperture,
    it assumes a variety of shapes, and in some is cup-shaped, in others
    forked, and in some forms a little angular shelf. Indeed, the
    variations are so numerous that I think it would be better to throw the
    two genera into one, and then divide them into smaller groups. Some
    species of Calyptræa are farther removed from each other with respect
    to the characters of the septum and general form of the shell, than
    they are from the Crepidulæ. Fig. 239. Mediterranean, North and South
    America, East and West Indies, New South Wales, &c.

    CREPIDULINA. Bl. CRISTELLARIA, Lam. Microscopic.

    CRESEIS. Ranz. _Order_, Pteropoda, Lam.--_Descr._ Thin, fragile,
    transparent, pyramidal, pointed; with a dorsal ridge produced into a
    point at the edge of the aperture.--_Obs._ The species found in the
    Mediterranean is named C. Spinifera (fig. 222), from its resemblance to
    a thorn.

    CREUSIA. Leach. (_Creux_, se. Fr. a cavity.) _Fam._ Balanidea, Bl.
    _Order_, Sessile Cirripedes, Lam.--_Descr._ A depressed cone,
    consisting of four valves, supported upon, and jointed to, a cup-shaped
    cavity formed in the Madrepores, in which it resides. Aperture
    quadrilateral, closed by an operculum of four valves.--_Obs._ This
    genus is distinguished from Pyrgoma, which is supported on the edge of
    a similar cup-shaped cavity, by the paries being composed of four
    valves, whereas in Pyrgoma, it consists of a single piece. Fig. 28, C.
    Gregaria. East Indies.

    CRICOSTOMATA. Bl. The second family of Asiphonibranchiata, Bl. It is
    thus described: "shell equally (with the animal) variable in general
    form, but of which the aperture, always nearly round, is completely
    closed by the shelly or horny operculum; whorls few, and apex
    sublateral." This family agrees in some measure with the family
    Turbinacea of Lamarck, and with the genus Turbo in the system of
    Linnæus. It contains the genera Pleurotomaria, Delphinula, Turritella,
    Proto, Scalaria, Vermetus, Siliquaria, Magilus, Valvata, Cyclostoma,
    and Paludina.

    CRIOCERATITES. A genus composed of species of Ammonites, with
    disconnected whorls. C. Duvallii, fig. 482.

    CRIOPUS. Poli. CRANIA, Auct.

    CRISTACEA. Lam. The third family of Polythalamous Cephalopoda, Lam.
    This family is described as including shells of the following
    characters:--"Multilocular, flattened, nearly reniform; the chambers
    gradually increasing in length, as they approach the outer arched
    margin, and appearing to revolve round an eccentric, more or less
    marginal axis. The Cristacea contain the genera Renulina, Cristellaria,
    and Orbiculina."

    CRISTACEA. Bl. The third family of Polythalamia, Bl. containing the
    genera Crepidulina, (Cristellaria, Lam.) Oreas and Linthuris.

    CRISTARIA. Schum. DIPSAS Plicatus, Leach. ANODON tuberculatus, Fer.

    CRISTELLARIA. Lam. CREPIDULINA, Bl. _Fam._ Cristacea, Lam. and
    Bl.--_Descr._ Semidiscoidal, chambered; whorls contiguous, enlarging
    progressively; spire eccentric, sublateral; septa imperforate.
    Microscopic.

    CRYPTA. Humph. CREPIDULA, Lam.

    CRYPTELLA. Webb. ([Greek: Kruptô], to conceal.) TESTACELLUS Ambiguus of
    Ferrusac. Published in Sowerby's Genera of Shells as PARMACELLA
    calyculata.--_Descr._ A small patelliform shell, with a very short
    papillary spire; and the aperture irregularly expanded. Fig. 256.
    Canary Islands.

    CRYPTOCONCHUS. Bl. A genus composed of species of Chiton, the valves of
    which are covered by the integument, as Chiton porosus of Burrows. Ch.
    amiculatus of Pallas.

    CRYPTODIBRANCHIATA. Bl. The first order of the class Cephalophora, Bl.
    containing families of molluscous animals destitute of shells.

    CRYPTOSTOMA. Bl. Differs from SIGARETUS, Lam. principally in the soft
    parts of the animal. De Blainville remarks that he is acquainted with
    only two species (from the Indies), which he can with decision refer to
    the genus, but he thinks that many of the Lamarckian Sigareti may very
    probably be found to belong to it, as soon as the soft parts shall be
    known. The species which he figures is Cryptostoma Leachii. (Manuel de
    Malacologie, pl. 42. fig. 3.)

    CTENOCONCHA. Gray. Described as having many characters in common with
    the Solens, the teeth like Nucula, but the cartilage entirely external.
    SOLENELLA, Sow.?

    CUCULLÆA. Lam. (_Cucullus_, a hood.) _Fam._ Arcacea, Lam.--_Descr._
    Sub-quadrate, nearly equivalve, sub-equilateral, deep; hinge
    rectilinear, with a series of angular teeth, small near the umbones,
    larger and more oblique towards the extremities; umbones separated by a
    flat external area, on which the ligament is spread. Anterior muscular
    impression produced into a sharp-edged plate or ledge, projecting from
    the side of the shell. Posterior muscular impression flat and
    indistinct.--_Obs._ This genus very much resembles Arca in general
    form, but differs in the oblique, lengthened character of the remote
    teeth, and in the singularly prominent edge of the muscular impression.
    China. Fig. 133, C. Auriculifera.

    CUCUMIS. Klein. MARGINELLA, Auct.

    CULTELLUS. Species of LUTRARIA, Lam. which have the umbones placed near
    the extremity of the shell. _Ex._ L. Solenoides, fig. 78.

    CUMA. Humph. FUSUS and FASCIOLARIA, Lam.

    CUMINGIA. Sow. _Fam._ Mactracea, Lam.--_Descr._ Equivalve,
    inequilateral, transverse, rounded anteriorly, subrostrated
    posteriorly. Hinge with a central spoon-shaped cavity in each valve,
    containing the cartilage; a very small anterior cardinal tooth in each
    valve; two lateral teeth in one valve, none in the other: muscular
    impressions two in each valve, distant; palleal impression with a very
    large posterior sinus.--_Obs._ The species known at present are found
    in sand, in the fissures of rocks in Tropical climates. They resemble
    Erycina in general form and character, but differ in having the
    internal cartilage placed in a prominent spoon-shaped process, while
    that of Erycina is contained in a hollow which sinks under the umbones.
    This genus should be placed near Amphidesma. Cumingia mutica, fig. 87.

    CUNEIFORM. (_Cuneus_, a wedge.) Wedge-shaped, as Donax, fig. 108.

    CUNEUS. Megerle. VENUS Meroe, Linn. and similar species.

    CUNICULA. Sw. A sub-genus of Uniones, thus described:--"Ovate, oblong;
    bosses thick, but depressed; cardinal teeth moderate. C. planulata,
    patula, rubiginosa, secura, purpurascens."

    CURVED. Arched or bent. _Ex._ Dentalium, fig. 2.

    CURVULA. Rafinesque. A fossil imperfectly described as differing from
    Pinna, in being inequivalve.

    CUVIERIA. Ranz. (Baron Cuvier.) _Class_, Pteropoda, Lam.--_Descr._
    Thin, transparent, glassy, cylindrical, rounded and inflated at the
    closed extremity, compressed towards the opening, so as to render it
    oval. This genus differs from Vaginula in being rounded, instead of
    pointed, at the lower extremity. Mediterranean. Fig. 223, C. Columella.

    CYCLAS. Brug. _Fam._ Conques Fluviatiles, Lam. Conchacea, Bl.--_Descr._
    Orbicular, thin, subovate, ventricose, sub-equilateral, equivalve;
    cardinal teeth minute, one more or less complicated in the left valve,
    two diverging in the right; lateral teeth elongated, compressed,
    laminar, acute, doubled in the left valve; ligament external; epidermis
    thin, horny.--_Obs._ The Cyclades are viviparous, and abound in
    ditches, ponds, slow streams, &c. in Europe and North America. The
    genus Pisidium has been separated on account of a difference in the
    animal, and may be known from Cyclas by being less equilateral, and the
    anterior side being the longest. Fig. 111, C. Rivicola.

    CYCLOBRANCHIATA. Bl. The third order of the second section of
    Paracephalophora Monoica, Bl. containing no genera of Testaceous
    Mollusca.

    CYCLOCANTHA. Sw. A genus of "Trochidæ," consisting of Turbo stellaris
    and T. Calcar, and corresponding with the genus Calcar, Montf.

    CYCLONASSA. Sw. A genus of "Nassinæ," Sw. consisting of Nassa
    Neritoidea, and corresponding with the genus Cyclops, Montf.

    CYCLOPHORUS. Montf. A generic name proposed for those species of
    Cyclostoma, Auct. which have an umbilicus. C. Involvulus, fig. 304,
    would be the type of this genus.

    CYCLOPS. Montf. NASSA Neritoidea, Auct. fig. 424.

    CYCLOSTOMA. Auct. ([Greek: kuklos], _cyclos_, round; [Greek: stoma],
    _stoma_, mouth.) _Fam._ Colimacea, Lam. Cricostomata, Bl. A genus of
    land shells varying in shape from that of Pupa to that of a flat orb;
    the aperture is generally circular and the peritreme uninterrupted,
    thickened and sometimes reflected, the operculum is shelly and spiral.
    Two other genera of land shells are provided with opercula, and
    consequently might be confounded with this genus. In Helicina, the
    operculum is concentric and the peritreme is not continuous; while in
    the small genus hitherto almost unknown of Pupina, the peritreme is not
    continuous and there is a glassy enamel over the whole of the external
    surface. In the plates we have represented, C. ferrugineum, fig. 303;
    C. involvulus, fig. 304.

    CYCLOTUS. Guild. A sub-genus of Cyclostoma, consisting of those species
    which are discoidal, as C. Planorbulum. Fig. 530.

    CYLINDER. Montf. CONUS textile, Auct. (fig. 461) and other species
    having a cylindrical form.

    CYLINDRELLA. Sw. A genus of the family "Ovulinæ," Sw. composed of
    cylindrical species of Ovulum? The wood-cut illustrating this genus has
    the appearance of a Bulla.

    CYLINDRICAL. ([Greek: kulindros], a cylinder.) This like other
    mathematical terms is used with great latitude by Conchologists, and
    applied to any shell the sides of which are nearly parallel, with the
    extremities either rounded, flat, or conical. _Ex._ Oliva, fig. 457.

    CYLLENE. Gray. _Fam._ Purpurifera, Lam.--_Descr._ Oval, thick, with a
    short acute spire; an oval aperture terminating anteriorly in a slight
    emargination, posteriorly in a short canal; a fold at the lower end of
    the body whorl; outer lip thick, striated within; angle of the whorls
    tuberculated.--_Obs._ This genus of small marine shells resembles
    Voluta in general character, but differs in having a smooth columella
    without folds. Recent, Pacific Ocean; Fosil, London clay. Fig. 425.

    CYMBA. Brod. (_Cymba_, a boat or skiff.) _Fam._ Columellaria,
    Lam.--_Descr._ Smooth, ventricose, with a very short, mammillated, rude
    spire; and a very large, wide aperture, terminated anteriorly in a deep
    emargination; posteriorly in a flat ledge, which separates the outer
    lip from the body whorl; columella with three or four oblique, laminar,
    projecting folds, terminating in a point; outer lip thin, with its edge
    sharp; epidermis smooth, brown, covered partly or entirely by the
    glassy enamel, which, commencing with the outer lip, spreads over the
    body of the shell.--_Obs._ These very elegant shells, found in Africa,
    are distinguished from the true Volutes by the shapeless, mammillated
    apex of the short spire, by the large size of the aperture, and by the
    horizontal ledge which separates the outer lip from the body whorl. The
    genus Melo, also separated by Mr. Broderip from the Volutes, agrees
    with Cymba in some respects, but differs in the regularity of the
    spire. Fig. 434, C. Porcina.

    CYMBIOLA. Sw. The generic name for a group of Volutes, described as
    "armed with spinous tubercules, sometimes smooth, but never ribbed;
    spiral whorls gradually diminishing in size, but not distorted; apex
    thick and obtuse; pillar with four plaits." Mr. Swainson remarks that
    this genus is chiefly distinguished by the obtuse, but not irregular
    spire. The typical species are stated to be V. Rutila and V.
    Vespertilio, fig. 433. Tropical.

    CYMBULIA. (Dim. from _Cymba_.) _Fam._ Pteropoda, Lam. An extremely
    light, cartilaginous covering of a molluscous animal, so named from its
    similarity in shape to a boat. We mention it here on account of its
    similarity to the shelly or glassy covering of other Pteropods, to
    which, although membranaceous, it is evidently analogous. The Cymbuliæ
    are found in the Mediterranean.

    CYPRÆA. Auct. _Fam._ Enroulées, Lam. Angyostomata, Bl.--_Descr._ Oval
    or oblong, ventricose, convolute, covered by an enamel, generally
    smooth and shining. Spire short, nearly hid. Aperture long, narrow,
    terminating in a short canal at both extremities. Outer lip dentated,
    thickened, inflected. Inner lip dentated, thickened, reflected over
    part of the body whorl.--_Obs._ These shells are so distinguished by
    the two rows of teeth arranged on each side of the aperture; the
    thickened front formed by the inner and outer lips; and the enamel
    deposited over the back of the shell from the mantle of the animal
    which envelopes it, that there is no danger of confounding them with
    any other genus, except in a young state. Before they have arrived at
    the full growth, the front is not thickened, and the outer lip is thin,
    not inflected, nor are the teeth formed. In this state the shell
    resembles, in some degree, an Oliva. Some species are striated, ribbed,
    or tuberculated, but the generality are smooth. Most species belong to
    tropical climates, only one to Great Britain. The C. Moneta is current
    as money in some parts of Africa, and many species are worn as
    ornaments by the South Sea Islanders. The colouring in most species is
    exceedingly rich, and arranged in every variety of spots, patches,
    rings, lines, bands and clouds. The species most esteemed by collectors
    are C. Mappa, C. Testudinaria, C. Pustulata, C. Aurora, C. Princeps, of
    which only two specimens are known, C. Leucodon, &c. See also
    Cypræovulum, Trivea and Luponia. The fossil species are principally
    from the Calc-grossier, the London Clay, Crag, &c. Fig. 445 to 450. The
    latest revision of this genus has been effected by Mr. G. B. Sowerby,
    sen., who has published a complete catalogue in his son's Conchological
    Illustrations. This catalogue enumerates 130 species, the whole of
    which are figured in parts 1 to 8, 101 to 131 of the above mentioned
    work.

    CYPRÆCASSIS. Stutch. (Cypræa and Cassis.)--_Descr._ Shell, when young,
    striated, reticulated, or tuberculated; outer lip simple: when mature,
    outer lip involute and toothed; columellar lip also toothed; aperture
    straight, anteriorly terminated by a recurved canal, posteriorly by a
    shallow channel. Animal with the mantle bilobed; operculum
    none.--_Obs._ The reasons given for separating this genus from Cassis,
    are, 1st, That the shells of the latter have an operculum, while those
    of the proposed genus have none. 2nd, That the Cypræcassides do not
    form a complete, thickened lip, before the full period of their growth,
    like the Cassides. 3rd, That the Cypræcassides have no epidermis. The
    species mentioned as probably belonging to Cypræcassis are C. rufa, the
    type; C. coarctata, and C. Testiculus, Auct. The establishment of this
    genus has been opposed on the ground that indications of epidermis are
    discoverable in some specimens of C. rufa; that some specimens of the
    same species and Testiculus have been examined, and found to have
    formed slightly thickened and dentulated outer lips at very early
    periods of growth, while many of the other Cassides are destitute of
    varices, and that an operculum of C. coarctata was brought to this
    country by Mr. Cuming. It is probable, however, that an increased
    knowledge of facts might go far to establish the separation. C.
    Testiculus, fig. 412.

    CYPRÆADIA. Sw. A genus of the family "Cypræidæ," Sw. thus
    described:--"Cypræform; the base contracted; the body whorl not
    flattened beneath; shell cancellated; aperture of equal breadth
    throughout; a few thickened, short teeth on the pillar; lip at the
    base, which is not internally concave. C. cancellata, Sw. Fossil only,
    differing from Trivea in its contracted base, in the inequality of its
    aperture, and the equal convexity of the inner lip within." (Sw. Lardn.
    Cyclop. Malac. p. 325.) Cyprædia, fig. 564.

    CYPRÆLA. Sw. A genus formed for the reception of Ovulum verrucosum,
    Auct. which has a circular depression at each extremity. It is the same
    as the genus Calpurnus of De Montfort. Ovulum verrucosum, fig. 441.

    CYPRÆOVULUM. Gray. A genus of Cypræidæ thus described, "shell like a
    cowry, but front end of columella covered with regular cross-ribs, like
    the rest of the base, internally produced into an acute toothed ridge.
    Shell pear-shaped, cross-ridged." C. capense, fig. 444. South Africa.

    CYPRICARDIA. Lam. _Fam._ Cardiacea, Lam.--_Descr._ Equivalve,
    inequilateral, subquadrate, transversely elongated, with the anterior
    side very short; hinge with three cardinal teeth and one remote lateral
    tooth in each valve; muscular impressions two in each valve; ligament
    external.--_Obs._ This genus is distinguished from Cardita by the three
    cardinal teeth. The mollusca of this genus are marine. C. angulata,
    fig. 125. Pacific Ocean.

    CYPRINA. Lam. _Fam._ "Conques Marines," or Marine Conchacea.--_Descr._
    Equivalve, inequilateral, sub-orbicular; umbones curved obliquely;
    hinge with three diverging cardinal and one remote lateral teeth in
    each valve; ligament external; muscular impressions two in each valve;
    palleal impression having a slight posterior sinus; epidermis thick,
    rough brown.--_Obs._ The Cyprinæ belong to the Northern hemisphere. The
    recent species are not numerous. Fossil species are found in the
    tertiary deposits. Cyprina may be known from Venus by the remote
    lateral tooth and the thick epidermis. C. vulgaris, fig. 116.

    CYRENA. Auct. _Fam._ Fluviatile Conchaceæ, Lam. Conchacea, Bl--_Descr._
    Suborbicular, equivalve, inequilateral, ventricose, corroded at the
    umbones, thick, covered with a thick epidermis; hinge with three
    cardinal and two remote lateral teeth in each valve. Muscular
    impressions two in each valve; palleal impression not sinuated.--_Obs._
    This genus is distinguished from Venus, Cytherea and Cyprina, by having
    two remote lateral teeth; and from Cyclas by the thickness of the
    shell. This genus is mostly fluviatile; the recent species are
    tropical, and the fossil are found in the newest formations. Fig. 113,
    C. fuscata.

    CYRENELLA. Desh. See CYRENOIDES.

    CYRENOIDES. Joannis. CYRENELLA, Desh. _Fam._ Conques Fluviatiles,
    Lam.--_Descr._ Equivalve, subequilateral, ventricose, thin, covered
    with a reddish brown epidermis, corroded at the umbones, with a slight
    posterior fold. Hinge thin, with three diverging cardinal teeth in each
    valve, and a very slight posterior fold in the right valve. Ligament
    not very tumid.--_Obs._ This fresh-water shell differs from Cyclas and
    Cyrena in the want of lateral teeth, and from the latter in the
    thinness of the shell. Fig. 114.

    CYRTIA. Dalman. ([Greek: Kurtos], curtos, gibbose.) _Fam._ Brachiopoda,
    Lam.--_Descr._ "Hinge rectilinear; with the back elevated into a
    semicone or half-pyramid, the cardinal side perpendicularly
    _plane_."--_Obs._ This genus of fossil Brachiopoda forms part of the
    genus Spirifer, Sow. C. exporrecta, (Anomites exporrecta, Nonnull.)
    fig. 204.

    CYTHEREA. Lam. _Fam._ "Conques Marines," Lam.--_Descr._ Equivalve,
    inæquilateral, oval, lenticular, or sub-trigonal; hinge with two or
    more short, diverging cardinal teeth, and one anterior approximate
    lateral tooth in each valve.--_Obs._ The Cythereæ are distinguished
    from the Veneres by the lateral tooth. C. Meretrix, fig. 117, and 117,
    _a. b. c. d._

    DACTYLUS. Humph. MARGINELLA, Auct.

    DARACIA. Gray. A subgenus of Pyrgoma, including a species which is
    remarkable for the irregularity of its form. It grows upon a species of
    Monticularia, and the margin takes the shape of the lobes by which it
    is surrounded. The aperture is large, and completely closed by the
    operculum. Daracia (Pyrgoma) Monticulariæ, fig. 489, 490.

    DATE. A common name given to shells of the genus Pholas, on account of
    their cylindrical form and consequent resemblance to the fruit. For the
    same reason the name Pholas Dactylus has been given by Naturalists to
    the species which we represent, fig. 66.

    DEAD SHELL. A term used among collectors to signify that the shell has
    been exposed on the sea-shore after the animal has ceased to live. A
    shell in this condition is worn down by attrition, and loses its beauty
    and brilliancy of colouring by being subject to the action of salt
    water. A dead shell may be known by a certain hoary whiteness spread
    over its surface.

    DECACERA. Bl. The second family of the order Cryptodibranchiata, Bl.
    containing the genera Calmar and Sepia, which have no shells.

    DECADOPECTEN. Rüppell. PECTEN _Plica_, Linn. Fig. 172, having a
    plicated hinge.

    DECOLLATED. (_Decollari_, to be beheaded.) The apex or nucleus of some
    shells being composed of a more fragile substance than the rest, has a
    tendency to fall off. The reason of this probably is that the animal
    withdrawing from that part, leaves it unprotected. When it falls off,
    the hole is stopped up by a septum filling the cavity of the volution,
    so as to exclude the air: the shell is then said to be decollated.
    _Ex._ Bulinus decollatus, fig. 289.

    DECUSSATED. Intersected by striæ crossing each other. _Ex._ Rissoa,
    fig. 346.

    DELPHINULA. Montf. (_Delphinus_, a dolphin.) _Fam._ Scalariens, Lam.
    Cricostomata, Bl.--_Descr._ Orbicular, depressed, thick, rugose; whorls
    few, angulated, branched at the angles; aperture pearly, rounded or
    sub-quadrate; peritreme continuous, thickened; operculum horny,
    composed of numerous whorls.--_Obs._ Several fossil species are found
    in the tertiary deposits. D. laciniata, fig. 352. Recent species belong
    to tropical climates.

    DELTHYRIS. Dalman. _Fam._ Brachiopoda, Lam.--_Descr._ Hinge more or
    less rounded, with distant umbones; both valves convex; with the umbo
    of the largest rostrated and deltoid, with a hollow. This genus forms
    part of the genus Spirifer, Sow. Fig. 205. D. Plycotes, Dalman.

    DELTOID. ([Greek: D], _delta_.) Triangular.

    DENDOSTREA. Sw. ([Greek: Dendron], _dendron_, tree; [Greek: ostreon],
    _ostreon_, oyster.) Ostrea _Crista-galli_, and other species which are
    attached to stems of sea-weed and corallines, by means of arms thrown
    out from the inner surface of the lower valve. Fig. 181, Ostrea Folium.

    DENTALIUM. Auct. (_Dens_, a tooth.) _Fam._ Maldania, Lam. _Order_,
    Cirrobranchiata, Bl.--_Descr._ Tubular, arched, increasing in size
    towards the anterior extremity, open at both ends; small aperture
    sometimes having a lateral fissure; large aperture round; external
    surface ribbed, striated or smooth.--_Obs._ The well known shells
    composing this genus are shaped very much like an elephant's tusk, and
    are not liable to be confounded with any other genus. The fossil
    species are sometimes termed Dentalithes, from _dens_, a tooth, and
    _lithos_, a stone. The Dentalia, being true molluscs, are not rightly
    placed among the Annelides. Fig. 2, D. octogonum. Found on sandy shores
    in most climates.

    DENTATED. Having teeth or raised points.

    DENTICULATED. (Denticulatus, Lat.) Having little teeth or raised
    points.

    DEPRESSED. Flattened, pressed down, as the spires of some shells.

    DEXTRAL Spiral Shells. Place the point of a spiral shell towards the
    eye, with its mouth downwards; if, as in most instances, the aperture
    be on the right side of the axis, it is a _dextral_ shell, if
    otherwise, it is _sinistral_ or _reversed_. Balea (fig. 296), and
    Clausilia (fig. 295), are examples of reversed shells.

    DEXTRAL Valve. Take a bivalve shell closed, place it before the eye,
    with the umbones uppermost, and the posterior side, which may be known
    by the ligament towards the observer, whose right side will then
    correspond with the right valve of the shell.

    DIADEMA. Ranz. CORONULA Diadema, Auct. fig. 17.

    DIANCHORA. Sow. _Fam._ Pectinides, Lam. _Order_, Palliobranchiata,
    Bl.--_Descr._ Inequivalve, attached, oblique, subtriangular; attached
    valve, having an opening in the place of the umbo; the other valve
    auriculated, with an obtuse umbo; hinge without teeth.--_Obs._ The
    green sand fossils contained in this genus differ from Plagiostoma in
    being attached. Fig. 175, D. striata.

    DIAPHANOUS. ([Greek: Dia], _dia_, through; [Greek: phainô], _phaino_,
    to shine.) Transparent.

    DIAPHRAGM, ([Greek: diaphragma], a partition.) This term is applied to
    the septa, by which the chambers of multilocular and other shells are
    divided from each other.

    DICERAS. Lam. ([Greek: Dis], _dis_, double; [Greek: Keras], _ceras_,
    horn.) _Fam._ Chamacea, Bl. and Lam.--_Descr._ Inequilateral,
    inequivalve, attached by the point of the umbo of the larger valve;
    umbones prominent, spirally twisted and grooved; hinge with one large
    thick tooth in the larger valve; muscular impressions, two in each
    valve.--_Obs._ The prominent spiral umbones, which give rise to the
    name of this genus, with the circumstance of its being attached by the
    point of one of them, is sufficient to distinguish it from any other,
    although it appears to approach Isocardia in some characters. In others
    it will be found still more nearly to resemble Chama. In fact, from
    being attached and irregular, the shells composing this genus have been
    considered as Chamæ with produced umbones. The singular fossil shells
    composing this genus, are found in granular limestone, near Geneva and
    in Normandy. Fig. 154, D. perversum.

    DIDONTA. Schum. SAXICAVA. Auct.

    DIFFUSE. (_Diffundo_, to spread out, to dilate.) A term applied to the
    aperture of a univalve shell, when it is spread out or widened into a
    flat surface, or digitations. _Alated_ is another term used to express
    the same character. Thus, the shells belonging to the family of Alatæ,
    in the system of Lamarck, are _diffuse_ in the outer lip. Fig. 402 to
    406.

    DIGITATED. (_Digitus_, finger.) Branched out in long points, as
    Ricinula, fig. 413.

    DILATED. Expanded, spread. This term has the same application as
    diffuse and alated, explained above. The outer lip of Rostellaria
    Columbaria, fig. 403 (Hippochrenes, Montf.), will serve as an example.

    DIMORPHINA. D'Orb. A genus of microscopic Foraminifera.

    DIMYARIA. ([Greek: Dis], _dis_, double; [Greek: muon], _myon_, muscle.)
    The first order of Conchifera, Lam. including those molluscs which have
    two adductor muscles, and consequently two muscular impressions in each
    valve. The Conchifera Dimyaria are divided into Crassipedes,
    Tenuipedes, Lamellipedes, and Ambiguæ, fig. 44 to 155.

    DIOICA. Bl. The first division of the class Paracephalophora, Bl. It is
    divided into the orders Siphonobranchiata and Asiphonibranchiata, Bl.

    DIPLODON. Spix. HYRIA Syrmatophora, Lam. fig. 144, and UNIO
    multistriatus, Lea, are doubtfully quoted by Lea as belonging to this
    apparently ill-defined genus of Nayades.

    DIPSAS. Leach. A genus or sub-genus of Nayades, the distinctive
    character of which is "having a linear tooth under the dorsal edge." D.
    plicatus, fig. 142.

    DISCINA. Lam. ORBICULA, Auct.

    DISCODOMA. Sw. A sub-genus of Lucerninæ, Sw. (Helix), thus described,
    "teeth none; aperture angulated; the inner lip nearly obsolete; the
    outer only slightly thickened; margin carinated."

    DISCOIDAL. (_Discus_, a circular plane.) A spiral shell is said to be
    discoidal, when the whorls are so horizontally convolute as to form a
    flattened spire. _Ex._ Planorbis, fig. 311. Orbulites Discus, fig. 479.

    DISCOLITES. Montf. A genus of microscopic Foraminifera.

    DISCONTINUOUS. Interrupted. _Ex._ The siphon of Nautilus is
    discontinuous, i. e. its termination in one chamber does not reach to
    its commencement in the next. The varices of Triton, occurring in
    different parts of the whorls, do not form the continuous ridges which
    characterize the generality of the Ranellæ.

    DISCORBITES. Lam. A genus of microscopic Foraminifera.

    DISTANT. The teeth on the hinge of a bivalve shell are said to be
    distant when they are remote from the umbones.

    DIVARICATED. Diverging, meeting in a point, as the teeth on the hinge
    of Placuna, fig. 184.

    DOLABELLA. Lam. (Dim. from _Dolabra_, a hatchet.) _Fam._ Aplysiacea,
    Lam. and Bl.--_Descr._ Hatchet-shaped, arched, covered with a horny
    epidermis; posteriorly attenuated, thickened, sub-spiral, anteriorly
    plane, broad, thin; posterior margin reflected.--_Obs._ The two or
    three species of Dolabella known are inhabitants of the Indian Ocean.
    They were placed by Linnæus in his very convenient genus Bulla, under
    the name B. dubia. Fig. 255, Dolabella Rumphii.

    DOLIUM. D'Argenville. (_a tun._) _Fam._ Purpurifera, Lam.
    Entomostomata, Bl.--_Descr._ Thin, ventricose, oval, or globular, with
    a short spire; large aperture terminating in a reflected canal, and
    spirally ribbed or grooved external surface; outer lip crenated; inner
    lip reflected over part of the body whorl, which terminates in a tumid
    varix; epidermis light, horny. Mediterranean and East Indian.--_Obs._
    This genus is distinguished from Cassis by the outer lip, which is not
    reflected. The species which are not so rotund as the others, as D.
    Perdix, Auct. have been separated under the name Perdix, as generic.
    Fig. 420, Dolium Maculatum.

    DONAX. Auct. _Fam._ Nymphacea, Lam. Conchacea, Bl.--_Descr._ Equivalve,
    inequilateral, trigonal, with the anterior side short, straight, plane;
    the posterior side elongated, drawn to a narrow, rounded termination;
    hinge with two cardinal teeth in one valve, one in the other, and one
    or two, more or less remote lateral teeth; ligament external; muscular
    impressions two in each valve; palleal impression sinuated
    posteriorly.--_Obs._ The Capsæ have not the crenated margins, the short
    anterior side, and the distinct lateral teeth, which characterize the
    Donaces. Some species of Erycina resemble Donax in general form, but
    are at once distinguished by the ligamentary pit in the hinge. Sandy
    shores in all climates. Fig. 108, D. cuneatus.

    DORSAL. A dorsal shell is one placed upon the back of the animal. The
    dorsal margin of a bivalve shell is that on which the hinge is placed;
    the opposite margins are termed ventral. The dorsal surface of a spiral
    univalve is that which is seen when the aperture is turned from the
    observer. The dorsal valve is the uppermost in Brachiopodous bivalves.
    The dorsal part of a symmetrical convolute univalve, such as the
    Nautilus and Ammonite is that part of the whorls which is at the
    greatest distance from the spire, that is, the outer part of the
    whorls. Thus the situation of the siphon is said to be dorsal when it
    pierces the septum near the outer edge of the whorls. The dorsal part
    of symmetrical conical univalves, such as Patella, is the upper part,
    on which the apex is placed.

    DORSALIA. Lam. (_Dorsum_, the back.) The first family of the order
    Annelides Sedentaria, Lam. containing the genera Arenicola, not a
    shell, and Siliquaria, fig. 1, which is now considered as a true
    mollusc, and placed next to Vermetus.

    DOSINA. Schum. VENUS Verrucosa, Casina, and similar species. Fig. 119,
    a.

    DREISSINA. MYTILUS Polymorphus. Auct. fig. 159. This genus differs from
    Mytilus principally in the characters of the animal. The shell is
    characterized by a small septiform plate under the hinge within.
    Fluviatile, Europe and Africa.

    EBURNA. Lam. (_Eburneus_, ivory.) _Fam._ Purpurifera, Lam.
    Entomostomata, Bl.--_Descr._ Oval, thick, smooth, turrited,
    umbilicated; spire angulated, acute, nearly as long as the aperture;
    aperture oval, terminating anteriorly in a canal, posteriorly in a
    groove; outer lip slightly thickened with an anterior notch, which
    terminates in a spiral fold surrounding the body whorl; umbilicus
    generally covered by the thickened columellar lip.--_Obs._ The
    beautiful shells called ivory shells, which originally constituted part
    of this genus, are now placed in the genus Ancillaria by authors. They
    differ from the present genus Eburna, in having the sutures of the
    spire covered with a polished enamel. (A. glabrata, fig. 455.) The
    Eburnæ resemble in some respects the genus Buccinum, but a glance at
    the figure will enable the reader to distinguish a true Eburna from all
    other shells. Fig. 426 is Eburna Zeylanica. A catalogue of 9 species is
    given in part 20 of the Conchological Illustrations published by the
    Author, accompanied by figures of several species.

    ECHIDNIS. Montf. Described as a straight, chambered, annulated, fossil
    shell, computed from the extremely gradual increase in diameter of the
    fragments to be at least sixteen feet long. Found in marble from the
    Pyrenees.

    ECHINELLA. Sw. A sub-genus of Monodonta. Sw. Malac. page 352.

    EFFUSE. (_effundo_, to pour out.) The aperture of an univalve shell is
    said to be effuse when there is a notch in the margin which would
    suffer a liquid to escape, and thus prevent it being filled to the
    brim.

    EGEON. Montf. A genus of microscopic Foraminifera.

    EGERIA. Lea. (Contrib. to Geol. p. 49, pl. 1.) A genus of fossil
    bivalves, described as very variable in form, with or without lateral
    teeth, sometimes a crenated margin, &c. The only certain characters
    appear to be that they have two diverging cardinal teeth in each valve,
    one of which is bifid; and an external ligament. Lea states that the
    Egeriæ should be placed between the Sanguinolariæ and the Psammobiæ,
    which two latter genera have been united by Sowerby. Fig. 103, E.
    Triangulata, from the tertiary formation of Alabama.

    ELENCHUS. Humph. A genus composed of TROCHUS Iris, Auct. and other
    similarly formed species. It is the same as CANTHARIDUS of Montfort.

    ELEPHANT'S TUSK. The common name given by dealers to shells of the
    genus Dentalium. _Ex._ D. octogonum, fig. 2.

    ELEVATED. A term which is applied by some conchological writers to the
    spire of an univalve shell when it consists of numerous whorls drawn
    out into a telescopic form. Other authors use the term _elongated_, or
    the more simple one '_long_,' to express the degree of elevation.

    ELISMA. Leach. A sub-genus of Bulinus. B. acutus, Auct. Gray, Turton,
    p. 185.

    ELLIPSOLITHES. Montf. ([Greek: Elleipsis], _ellipsis_, oval; [Greek:
    lithos,] _lithos_, stone.) A genus composed of Ammonites, which instead
    of being regularly orbicular, take an elliptical or oval form. This
    character appears to be accidental, as some individuals of the same
    species, both of Nautilus and Ammonites, are round, while others are
    compressed into an oval form.

    ELLIPSOSTOMATA. Bl. ([Greek: Elleipsis], _ellipsis_, oval; [Greek:
    stôma], _mouth_.) The third family of the class Asiphonibranchiata, Bl.
    The shells of this family are described as of various forms, generally
    smooth; the aperture longitudinally or transversely oval, completely
    closed by a horny or shelly operculum. This family contains the genera
    Rissoa, Phasianella, Ampullaria, Helicina, and Pleuroceras.

    ELLIPTICAL. ([Greek: Elleipsis], _ellipsis_.) Oval. Applied to any
    shell or part of a shell, having that form.

    ELMINEUS. Leach. _Order_, Sessile Cirripedes, Lam.--_Descr._ Four
    unequal valves, arranged circularly side by side, forming a quadrate
    cone; aperture large, sub-quadrate, irregular; operculum composed of
    four valves, in pairs.--_Obs._ This genus differs from Conia in the
    structure of the shell, the latter being porous. Fig. 22, Elmineus
    Leachii.

    ELPHIDIUM. Montf. (Conch. Syst. t. 1. p. 15.) A genus of microscopic
    Foraminifera.

    EMARGINATED. (_e_, out; _margo_, border.) Notched or hollowed out.
    Applied to the edges or margins of shells, when instead of being level
    they are hollowed out, as the outer lip of Oliva, fig. 457, at the
    base, and the ventral margins of some bivalves.

    EMARGINULA. Lam. (_e_, out; _margo_, border.) _Fam._ Calyptracea, Lam.
    Branchifera, Bl.--_Descr._ Patelliform, oblong or oval; anterior margin
    notched or emarginated; apex posteriorly inclined; muscular impressions
    wide.--_Obs._ Emarginula elongata, of some Authors, PARMOPHORUS of De
    Blainville is commonly called the Duck's bill limpet, from its shape.
    The Emarginulæ may be known from Patellæ and other neighbouring genera,
    by the notch or slit in the anterior edge. In the genus Rimula, Defr.
    fig. 243, this slit is near the apex, and does not reach the margin.
    Recent species occur in all climates, but are not numerous. Fossil
    species are still more rare, occurring in the Calc-grossièr, Crag and
    Oolite. E. fissurata, fig. 241.

    ENA. Leach. A sub-genus of Bulinus. B. Lackhamensis. Mont.

    ENDOSIPHONITES. A genus composed of Ammonites, having the siphon close
    to the body whorl, fig. 476.

    ENDOTOMA. Rafinesque. A genus of microscopic Foraminifera.

    ENROULEES. Lam. See CONVOLUTÆ.

    ENSATELLA. Sw. A genus consisting of SOLEN ensis, Auct. fig. 60, and
    other species similarly curved. _Genus_ ENSIS, Schum.

    ENSIS. Schum. SOLEN ensis, Auct. and similar species.

    ENTALIS. Defr. DENTALIUM duplicatum, Bl. PHARETRIUM, König. This genus
    is described as a small tube, within a larger one, the smaller
    extremity of the inner tube projecting beyond that of the outer one.
    Deshayes, who describes this genus, expresses a conviction that the
    soft parts of the animal must be entirely different from those of the
    animal of Dentalium. The genus PHARETRIUM, as described by König in his
    "Icones Fossilium Sectiles," is evidently identical with Entalis. It is
    placed by him in the family of Pteropoda, but being a fossil shell,
    there is some difficulty in finding its place in the system. See
    plates, fig. 3.

    ENTELLITES. Fischer. A genus composed of species of TEREBRATULA,
    SPIRIFER, and PRODUCTUS, Auct. having the hinge large and the umbones
    short. ORTHIS? Dalman.

    ENTIRE. (Integra.) Not interrupted, not emarginated. The peritrême of a
    univalve shell is said to be entire when not interrupted by canals or
    by the body whorl. _Ex._ Cyclostoma, fig. 304. The palleal impression
    is entire, when continued without interruption, or without a sinus.

    ENTOMOSTOMATA. Bl. The second family of the order Siphonibranchiata,
    Bl. The shells of this family are described as differing but little
    from those contained in the family of Siphonostomata of the same
    author, both with regard to the soft parts, and their testaceous
    covering. This family partly answers to the Purpuriferæ in the system
    of Lamarck, and contains the genera Subula, Cerithium, Melanopsis,
    Planaxis, Terebra, Eburna, Buccinum, Harpa, Dolium, Cassidaria, Cassis,
    Ricinula, Cancellaria, Purpura, Concholepas.

    EOLIDES. Montf. A genus of microscopic Foraminifera.

    EPIDERMIS. ([Greek: Epi], _epi_, over or upon; [Greek: derma], _derma_,
    skin.) The fibrous, horny, external coating of shells, called by the
    French, "_Drap marin_," or marine cloth. Lamarck objects to the name
    Epidermis because he does not consider the substance as answering to
    the cuticle or scarf skin of the human body, but more analogous to the
    nails and hair. Gray calls it the PERIOSTRACUM, from the membranous
    skin covering the bones of quadrupeds.

    EPIPHRAGM. The membranaceous or calcareous substance by which some
    species of molluscs close the aperture of the shell, when they retire
    within it to hibernate. When the animal wishes to come forth from his
    hiding-place, again to breathe the air, the edges of the Epiphragm are
    detached by a chemical process, so that it drops off. The name
    Hibernaculum has also been given to this covering. It must not be
    confounded with the operculum, which is a permanent portion of the
    shell, and is used as a door, fitted to the foot of the animal and
    moved at will to open or close the aperture of the shell, whereas the
    Epiphragm is produced for the occasion from a mucous secretion of the
    animal and dissolved at the edges when no longer wanted, when it drops
    off.

    EPISTYLA. Sw. A subgenus of the genus HELIX. E. conical. Sw. Helix
    Epistylium, fig. 281.

    EPONIDES. Montf. A genus of microscopic Foraminifera.

    EQUILATERAL. (Æquus, equal; latus, side.) Equal-sided. A term applied
    to bivalve shells, when a line drawn down perpendicularly from the apex
    would divide the shell into two equal parts. _Ex._ Pectunculus pilosus,
    fig. 134.

    EQUIVALVE. (Æquus, equal; _valva_, a valve.) A term applied to a
    bivalve shell when the valves are equal to each other in dimensions.

    ERATO. Risso. _Fam._ Convolutæ, Lam.--_Descr._ Ovate, more or less
    angulated, smooth or granulated, with a dorsal scar; spire short;
    aperture large, angulated, emarginated; columella slightly crenated;
    outer lip reflected, denticulated on the inner edge. Suture of the
    whorls covered with enamel.--_Obs._ This genus of shells resembles
    Marginella in form, but has no folds on the columella. Having a scar or
    groove down the back it may be considered intermediate between
    Marginella and Cypræa. Fig. 454, E. Maugeriæ. In the Author's
    Conchological Illustrations, seven species are enumerated and figured.

    ERUCA. Sw. A subgenus of Clausilia. Sw. Malac. p. 334.

    ERVILIA. Turt. A genus described as "oval, equivalve, equilateral,
    closed. Hinge with a single erect tooth closing between two small
    diverging ones in the opposite valve: lateral teeth none. Ligament
    internal. E. nitens. Turt. Mya. nitens, Auct."

    ERYCINA. Lam. _Fam._ Mactracea, Lam. Conchacea, Bl.--_Descr._ Ovate or
    triangular, transverse, equivalve, inequilateral, smooth; hinge with a
    ligamentary pit, two diverging cardinal and two lateral teeth in each
    valve; muscular impressions two in each valve; palleal impressions
    sinuated. East and West Indies and Mediterranean.--_Obs._ This genus is
    distinguished from _Mactra_ and _Lutraria_ by the cardinal teeth being
    placed one on each side of the ligamentiferous pit; whereas in the last
    named genera they are both placed on the anterior side. Fig. 86, E.
    Plebeja.

    ERYTHRÆA. The ancient name for CYPRÆA.

    ESCUTCHEON. The impression on the posterior dorsal margin of some
    bivalve shells. That on the anterior margin is named the lunule. The
    escutcheon is pointed out by the letter _e_ in some of the figures of
    Cythereæ. Fig. 117, _a. b. c._

    ETHERIA. Lam. (_Æther_, air.) Fam. Chamacea, Lam. and Bl.--_Descr._
    Irregular, inequivalve, inequilateral, foliaceous, pearly within,
    covered by an olive green epidermis without; hinge callous, undulated,
    destitute of teeth; ligament partly external, partly internal, passing
    through the hinge on a somewhat raised, callous area in the lower
    valve. Muscular impressions elongated, two in each valve, united by a
    slender palleal impression. Rivers of Africa.--_Obs._ The irregular,
    unequal air-bubbles of the inner surface, whence this genus derives its
    name, are very brilliant in some species, and atone, in some measure,
    for the rugged ugliness of the exterior. In its irregular form,
    foliated structure, and toothless hinge, it resembles OSTREA, from
    which it differs in having two muscular impressions. Fig. 155, E.
    semilunata.

    EULIMA. Risso. _Fam._ Scalariens, Lam.--_Descr._ Elongated, smooth,
    pyramidal; spire long, composed of numerous whorls; apex acute,
    slightly tortuous; aperture oval, rounded anteriorly, acute at the
    posterior union with the body whorl; outer lip slightly thickened;
    columella smooth. Fig. 347, E. labiosa, fig. 348, E. splendidula. A
    complete illustrated monograph of this genus of pretty shining little
    shells, consisting of 15 known species, is given in parts 52 and 53 of
    the Conchological Illustrations by the author.

    EUOMPHALUS. Sow. _Fam._ Scalariens, Lam.--_Descr._ Orbicular,
    planorbular spire, with three or four volutions, imbricated above;
    smooth below; aperture of a round polygonal form; umbilicus large,
    penetrating to the apex of the shell.--_Obs._ This genus of fossils
    very nearly resembles Delphinula. The main difference appears to be
    that the whorls do not increase so rapidly in size in the former as in
    the latter. Fossil, in the Carboniferous Limestone. Fig. 350.

    EXOGYRA. Sow. A genus of fossil bivalves, resembling Chama in shape and
    Ostræa in structure, having but one muscular impression in each valve.
    Fig. 183.

    EXSERTED. Standing out, protruding.

    EXTERNAL. An external shell is one which contains the animal, and is
    not covered by the mantle.

    FASCIATED. (_fascia_, a band.) Banded or striped. Ex. Carocolla
    marginata, fig. 277.

    FASCICULATED. (from fasciculum.) A little bunch of hairs or bristles
    against each end of each valve, characterizes some species of the genus
    Chiton, which are termed fasciculated species.

    FASCIOLARIA. Lam. _Fam._ Canalifera, Lam. Siphonostomata, Bl.--_Descr._
    Elongated, fusiform, ventricose; spire conical, consisting of few
    rounded or angulated whorls; aperture wide, terminating in a long
    straight open canal: columella lip with several oblique folds, the
    lower of which is larger than the rest; operculum horny,
    pyriform.--_Obs._ This genus is known from Fusus by the folds on the
    columella; from Turbinella, by their obliquity and the last being
    larger than the rest. Fig. 386, F. Trapezium. East and West Indies and
    Australia.

    FAUNUS. Montf. MELANOPSIS, Auct.

    FERRUGINEOUS. Of an iron rust colour.

    FERUSSINA. Grateloup. STROPHOSTOMA, Deshayes.

    FIBROUS. A shell is said to be of a fibrous structure when a fracture
    would present a series of perpendicular fibres, as Pinna.

    FICULA. Sw. A generic group of shells, consisting of those species of
    PYRULA, Auct. which have the true pear-shaped character. Fig. 390, P.
    Ficus. Sowerby confines the name Pyrula to these species.

    FIMBRIA. Megerle. CORBIS, Lam.

    FIMBRIATED. Fringed; as Murex fimbriatus, a delicate white species,
    with broad fringed varices.

    FISSURE. (_Fissura_, a slit.) A slit or cut, a narrow perforation, as
    in Emarginula and Fissurella.

    FISSURELLA. Brug. (_Fissura_, a fissure.) _Fam._ Calyptracia, Lam.
    Branchifera, Bl.--_Descr._ Patelliform, oval or oblong, radiated; apex
    anterior, perforated.--_Obs._ The Fissurellæ are known from Patellæ by
    the perforation in the apex. Fig. 245. The catalogue published by the
    author in the Conchological Illustrations, enumerates 68 species.

    FISTULANA. Lam. (_Fistula_, a pipe.) _Fam._ Tubicolæ, Lam. Adesmacea,
    Bl.--_Descr._ A transversely elongated, equivalve, inequilateral
    bivalve, enclosed by a septum within the widest, closed extremity of a
    straight calcareous tube. Fistulana is known from Gastrochæna by the
    straightness of the tubes, and the oblong state of the valves. Fig. 54,
    Fistulana Clava.

    FLEXUOUS. Having windings or bendings. _Ex._ The Tellinæ are known by
    the twist or flexuosity in the posterior ventral margin of the shell.

    FLORILLUS. Montf. A genus of microscopic Foraminifera.

    FLUVIATILE. (Fluviatilis.) Belonging to a river or running stream.
    _Ex._ Limnæa fluviatilis.

    FLUVIATILE CONCHACEA. See CONCHACEA.

    FOLIATED, or FOLIACEOUS. (From _folium_, a leaf.) When the edges of the
    successive layers of which a shell is composed are not compacted but
    placed apart from each other, projecting like tiles, the shell is said
    to be of a foliated structure. The common Oyster, fig. 180, presents a
    familiar example.

    FORAMINIFERA. D'Orb. (_Foramen_, a hole or pit.) An order established
    for minute many chambered internal shells, which have no open chamber
    beyond the last partition. Lamarck, D'Orbigny, and other writers have
    placed them among the Cephalopoda in their systems, but Du Jardin, on
    comparing the fossils with some recent species of the same class,
    arrived at the conclusion, now generally adopted, that they constitute
    a distinct class, much lower in degree of organization than even the
    Radiata. Not recognizing these microscopic bodies as shells, properly
    so called, but considering them sufficiently numerous and interesting
    to form a distinct branch of study, I do not think it desirable to
    describe the genera, or to present any arrangement of them in this
    work.

    FORNICATED. Arched or vaulted, as the exfoliations on the costæ of
    Tridacna Elongata, fig. 157.

    FOSSIL SHELL. A shell is considered to be in a fossil state when, the
    soft parts having ceased to exist, it is deprived of all its animal
    juices, has lost all, or nearly all its natural colour, and is thus
    changed in its chemical composition, when little or nothing is left but
    a mere bone, which is embedded in a sedimentary deposit. In this state,
    it is fragile, prehensile to the tongue, and either destitute of colour
    or tinged with the diluted mineral matters which pervade the stratum in
    which it lies. In some cases, the mineral composition of the shell is
    so completely changed as no longer to present its proper structure,
    consisting of successive oblique layers of shelly matter; but is
    altered into a fibrous structure, composed of rhomboidal particles. An
    example of this will be found in the Belemnites, which if broken, shew
    the perpendicular fibres. In other cases, the matter which has entered
    and filled up the cavities of the shell has become silicified, or
    changed into flint, and the shell itself has been decomposed and fallen
    off, so as to leave nothing but an external or internal cast of its
    form, in flint. This is called a Conchyliomorphite by continental
    writers. Some of the most important of Geological data are obtained by
    a minute comparison of fossil shells, found in various beds, with
    recent ones presenting the nearest resemblance to them. Some species of
    fossil shells are considered as identical with recent species. And many
    Geologists seek to fix the chronology of the different strata by the
    number of species which they inclose bearing a resemblance to the
    recent species. Indeed, all who would study Geology with success, will
    find it indispensably necessary to obtain a thorough knowledge of
    Conchology.

    FRAGELLA. Sw. A sub-genus of Monodonta, corresponding with the genus
    Clanculus, Montf. consisting of M. Pharaonis (fig. 361), and similar
    species. Sw. p. 352.

    FRAGILE. (_Fragilis._) Tender, easily broken.

    FREE SHELL. One that is not attached.

    FREE VALVE. In attached bivalve shells, one only is fixed; the other is
    then _free_, as far as to the action of opening and shutting.

    FRESH-WATER SHELLS, (sometimes described as aquatic) are those which
    either inhabit rivers, running pools and ditches, in which case they
    are _fluviatile_; or wells and ponds of standing water, &c. Fresh-water
    shells are either thin and horny in their texture, as the Limneana of
    Lamarck; or are covered with a compact, smooth, horny epidermis. They
    are generally simple in form, subject to corrosion where the epidermis
    is wounded or broken, and are circumscribed with regard to the classes
    and genera to which they belong. The family of Nayades includes nearly
    all the fresh-water bivalves; and the Melaniana and Limneana are the
    principal among univalves.

    FRONDICULARIA. Defr. A genus of microscopic Foraminifera.

    FRONT. The surface of a shell on which the aperture appears.

    FULCRUM. That part of a shell on which any other part rests or turns.
    The term is applied more particularly to the tumid part in the hinge of
    bivalve shells on which the ligament is fixed.

    FULGUR. Montf. PYRULA perversa, Auct. and such other species as have an
    angulated spire. Fig. 388.

    FUSIFORM. (_Fusus_, a spindle.) Shaped like a spindle, swelling in the
    centre and tapering at the extremities. _Ex._ Fusus, fig. 387.

    FUSUS. Brug. (A spindle.) _Fam._ Canalifera, Lam. Siphonostomata,
    Bl.--_Descr._ Fusiform, turrited, with many rounded whorls; aperture
    generally oval, terminating in a long straight canal; operculum horny,
    pyriform.--_Obs._ The Fusi are subject to considerable variations in
    form. The recent species are numerous and do not appear to be confined
    to any climate. The fossil species are also numerous, chiefly abounding
    in the tertiary formations. The recent species are mostly tropical.
    Fig. 387, F. Colus.

    GALATHÆA. Brug. POTAMOPHILA, Sow. MEGADESMA, Bowd.

    GALEA. Klein. PURPURA, Auct.

    GALEOLARIA. Lam. (From Galea, a helmet or crest.) A genus composed of
    species of SERPULA, Auct. Distinguished as being fixed by the side of
    the shell, and having the anterior extremity erect, the aperture
    terminating in a tongue-shaped projection.--_Obs._ This genus is said
    by Lamarck to resemble Vermilia in other respects, but to differ in
    having the anterior part raised. Fig. 6, G. decumbens. Africa and
    Australia.

    GALEOMMA. Turt. _Fam._ PHOLADARIA, Lam.--_Descr._ Thin, oval,
    equivalve, equilateral, with the ventral margin gaping; hinge with one
    cardinal tooth in each valve; muscular impressions two, approximate;
    palleal impression interrupted, not sinuated; ligament small, partly
    internal, partly external, fixed on a prominent fulcrum.--_Obs._ The
    wide hiatus in the ventral margins of this equilateral shell prevents
    the possibility of confounding it with any other. Four or five recent
    species are known, one of which is found on the coast of Sicily, and
    also in the British Channel. G. Turtoni, fig. 58.

    GALERICULUS. (_Galericulum_, a little cap or bonnet.) VELUTINA, Auct.
    fig. 337.

    GALERUS. Humph. CALYPTRÆA, Lam.

    GAPING. (_Hians._) Bivalve shells are said to gape when the margins do
    not meet all round. _Ex._ Gastrochæna, fig. 52.

    GARI. Schum. PSAMMOBIA, Lam.

    GASTEROPODA. Lam. ([Greek: Gastêr], _gaster_, belly; [Greek: pous,
    podos], _pus_, _podos_, a foot.) The second order of the class
    Mollusca, Lam. containing those molluscous animals whose organs of
    locomotion are ventral. Most of the shells belonging to this order are
    patelliform, placed upon the back of the animals, which rest or crawl
    upon the belly. This order is divided into Pneumonobranchiata, that is,
    those which breath air, or land molluscs; and Hydrobranchiata, or those
    which breath water, marine or fresh-water molluscs. Fig. 227 to 263.

    GASTRANEA. Schum.? CORBULA, Auct.

    GASTROCHÆNA. Speng. ([Greek: Gastêr], _gaster_, belly; [Greek: chaino],
    _chaino_, gape.) _Fam._ Pholadaria, Lam. Pyloridea, Bl.--_Descr._
    Equivalve, regular, inequilateral, with a wide, oblique, ventral
    hiatus, enclosed in a curved pyriform tube. Differing from Galeomma in
    being a free, oblique shell; from Fistulana, in the oval shape of the
    valves, and the curve of the tube; from Aspergillum and Clavagella, in
    both valves being free.--_Obs._ The Gastrochænæ are found in the
    hollows of massive shells or other marine substances. Fig. 62, G.
    Modiolina.

    GASTROPLAX. Bl. UMBRELLA, Lam. De Blainville described this genus from
    a specimen in which the shell had been, probably by accident, placed
    upon the under part of the animal, and not discovering his error until
    afterwards, gave it the above name.

    GEOMITRA. Sw. A sub-genus of Geotrochus, Sw. founded on a trochiform
    species of Helix, with coronated nodules on the whorls. Helix
    bicarinata, Sow. Zool. Journ. 1, pl. 3, fig. 7. Sw. page 166 and 332.

    GEOPHONUS. Montf. Conch. Syst. t. 1, p. 19. A genus of microscopic
    Foraminifera.

    GEOTROCHUS. Sw. HELIX pileus, Auct. (fig. 278,) and other trochiform
    species. Divided into the sub-genera Pithohelix, Geotrochus,
    Hemitrochus, Gonidormus, and Geomitra. Sw. p. 165 and 166, described at
    page 331.

    GEOVULA. Sw. A sub-genus of Melampus (Auricula), consisting of oval
    species, resembling Auricula Midæ, fig. 297.

    GERVILLIA. Defr. _Fam._ Margaritacea, Bl. Malleacea, Lam.--_Descr._
    Equivalve, oblong, oblique; hinge long, straight, having small,
    irregular, transverse ligamentary pits.--_Obs._ This genus of fossil
    shells, found at various geological periods, from the Lias to the
    Baculite limestone in Normandy, is now extinct. In general form it
    resembles Avicula, but in the hinge it approaches Perna. Fig. 169, G.
    Avicularis.

    GIBERULA. Sw. A genus separated from MARGINELLA, Auct. and thus
    described, "sub-oval; spire slightly prominent; top of the outer lip
    dilated and gibbous; base of the inner lip with plaits; inner lip
    broad, spreading. G. Zonata. Enc. Méth. 374, f. 6."

    GIBBOSE or GIBBOUS. (_Gibbosus._) Bunched out, embossed, having a lump
    or swelling of any kind. _Ex._ Bulinus Lyonetianus, (fig. 284.) named
    Gibbus by De Montfort. Ovulum gibbosum.

    GIBBUS. Montf. BULINUS _Lyonetianus_, Lam. PUPA, Bl. fig. 284.

    GIOENIA. A name given in the Encyclopédie Méthodique, to the plates of
    the stomach of Bulla Lignaria.

    GLABELLA. Sw. MARGINELLA Glabella (fig. 437), Goodallii, Auct. and
    similar species.

    GLANDINA. Schum. POLYPHEMUS, Montf.

    GLANDIOLUS. Montf. A genus of microscopic Foraminifera.

    GLAUCONOME. Gray. _Fam._ Solenacea, Lam.--_Descr._ Oblong or oval,
    transverse, slightly ventricose, equivalve, inequilateral; margins
    close, rounded anteriorly, somewhat acuminated posteriorly; hinge
    teeth, three in each valve, of which the central in one, and the
    posterior in the other, are bifid; muscular impressions anterior,
    elongated, marginal; posterior sub-quadrate; palleal impression, having
    a long sinus; ligament oblong, external; epidermis thin, horny, green,
    folded over the margins.--_Obs._ This shell, of which only one species
    is known, inhabits some of the rivers in China. C. Chinensis, fig. 64.

    GLOBIGENERA. D'Orb. A genus of microscopic Foraminifera.

    GLOBOSE. (_Globosus._) Rounded like a globe or ball, as the species of
    Helix, represented in fig. 268.

    GLOBULARIA. Sw. A sub-genus of Natica, consisting of globose species.
    (Sw. p. 345.) _Ex._ N. Lineata, fig. 328.

    GLOBULUS. Sow. Min. Con. AMPULLARIA, Auct.

    GLYCIMERIS. Lam. _Fam._ Solenacea, Lam. Pyloridea, Bl.--_Descr._
    Equivalve, transverse, oblong, thick, compressed, gaping at both
    extremities; hinge callous, without teeth; ligament large, external,
    prominent; epidermis thick, black, horny, folded over the margins;
    muscular impressions two, distant, running into the irregular palleal
    impression which unites them.--_Obs._ But few species of this singular
    genus are known; Lamarck describes two species from the Northern Seas.
    Blainville is of opinion that they belong to the family of the Nayades.
    Fig. 67, G. Siliqua.

    GNATHODON. Gray. ([Greek: Gnathos], _gnathos_, jaw-bone; [Greek: odos],
    [Greek: odontos], _odontos_, tooth.) _Fam._ Mactracea, Lam.--_Descr._
    Ovate, posteriorly angulated, equivalve, thick, ventricose,
    inequilateral, covered with a greenish brown epidermis; umbo distant,
    prominent; hinge having in one valve a sharp, angular, notched,
    cardinal tooth, and two lateral teeth, the posterior of which is
    elongated, and the anterior angulated, tortuous, shaped like a
    jaw-bone; in the other valve, two cardinal and two lateral teeth, the
    anterior of which is wedge-shaped; ligament internal, cuneiform, placed
    in a deep cardinal pit proceeding from the umbones; muscular
    impressions two; palleal impression having a slight sinus.--_Obs._ Only
    one species is known, G. cuneatus, fig. 83, from New Orleans. It is
    known from all other shells by the character of the hinge.

    GONIATITES. De Haan. A genus composed of species of Ammonites, Auct. in
    which the last whorl covers the spire and the sinuations of the septa
    are angulated. Fig. 480, G. striatus.

    GONIDOMUS. Sw. A sub-genus of Geotrochus, Sw. PUPA pagodus, Auct. Sw.
    p. 332.

    GONIOSTOMA. Sw. A sub-genus of Bulimus, thus described, "spire
    elongated, of few whorls; aperture contracted at each end; lips
    margined; the pillar curving inwards; the base slightly notched. G.
    erubescens, _Sw._ Zool. Journ. i. pl. 5, f. 2." Sw. p. 335.

    GONIOSTOMATÆ. Bl. A family belonging to the order Asiphonibranchiata,
    Bl. containing the genera Solarium and Trochus.

    GONOSPIRA. Sw. A sub-genus of Pupa, thus described, "spire perfectly
    cylindrical, of equal thickness, the tip obtuse, with the whorls large;
    aperture oval; lips thickened; pillar with or without a plait. G.
    polanga, _Desh._ Lesson, Voy. pl. 8, f. 8." Sw. p. 333.

    GRANULATED. (_Granum_, a grain.) Covered with minute grains, rough. The
    granulated lip of Oniscia, (fig. 409) will serve as an example.

    GRATELOUPIA. Moulins. _Fam._ Nymphacea, Lam.--_Descr._ Equivalve,
    inequilateral, sub-cuneiform, rounded anteriorly, sub-rostrated
    posteriorly; hinge with three cardinal teeth, a series of five or six
    irregular, small, diverging teeth behind the umbones, and one lateral
    anterior tooth in each valve; ligament external; muscular impressions
    two; palleal impression sinuated posteriorly.--_Obs._ This genus (Donax
    irregularis, Bast.) is only known in a fossil state. Fig. 102, G.
    Moulinsii.

    GRYPHÆA. Lam. (From Gryps, a griffin.) _Fam._ Ostracea, Lam.--_Descr._
    Inequivalve, free; lower valve large, concave; with the umbo prominent,
    incurved; upper valve small, flat, opercular; hinge toothless, with a
    curved, depressed area; one muscular impression.--_Obs_. These shells,
    which approach the Oysters, are of a more regular form, and are
    remarkable for the curved, produced beak of the lower valve. They are
    only known in a fossil state, belonging to the more ancient strata.
    Fig. 182, G. incurva. The recent species mentioned by Lamarck is not a
    true Gryphæa.

    GYMNOLEPAS. A generic name used by De Blainville to include OTION and
    CINERAS, Leach.

    GYMNOSOMATA. Bl. The second family of the order Aporobranchiata, in the
    system of De Blainville. The animals belonging to this family are
    destitute of shells.

    GYPIDEA. Dalman. A genus of Brachiopoda, thus described, "Larger valve
    with the umbo rostrated, remote from the hinge; with the canal large,
    deltoid; bilocular within." PENTAMERUS, Sow. Fig. 210. 211, G.
    Conchidium, copied from Dalman.

    GYROGONA. Lam. A genus of microscopic Foraminifera.

    GYROIDINA. D'Orb. A genus of microscopic Foraminifera.

    HALIOTIDÆ. Sw. A sub-genus of Calyptræa. CALYPTRÆA dilatata. Sowerby's
    Genera of Shells, fig. 9.

    HALIOTIS. Auct. ([Greek: als], _als_, sea; [Greek: ous], [Greek: ôtos],
    _otos_, ear.) _Fam._ Macrostomata, Lam. Otides, Bl.--_Descr._ Auriform,
    broad, depressed, pearly within, rough, costated, tuberculated without;
    spire short, flat, consisting of one or two whorls; aperture wide;
    ovate; columella laminar, flat, oblique; a spiral series of
    perforations running along the dorsal margin.--_Obs._ The splendid
    shells belonging to this genus are remarkable for the pearly
    iridescence of the inner surface, and the row of holes following the
    course of the spire. The soft parts are eaten in Guernsey and Jersey,
    and reckoned delicious. They belong to temperate and tropical climates.
    Fig. 338, H. rubra. 339, Padollus, Montf.

    HALIOTOID. (_Haliotis_ and [Greek: eidos], _eidos_, form.) Ear-shaped.

    HAMIFORM. (_Hamus_, a hook.) Curved at the extremity.

    HAMITES. Parkinson. (_Hamus_, a hook.) _Fam._ Ammonacea, Lam.--_Descr._
    Elongated, cylindrical, chambered, recurved at the smaller extremity,
    annulated; septa lobed and sinuated.--_Obs_. This remarkable fossil
    from the Baculite limestone in Normandy, differs from Baculites in
    being curved at one extremity, a circumstance from which its name is
    derived. Some small species are found in Chalk-Marle, Folkstone. Fig.
    484*. H. cylindricus.

    HARPA. Brug. (_Harpa_, a harp.) _Fam._ Purpurifera, Lam. Entomostomata,
    Bl.--_Descr._ Oval, ventricose, longitudinally and regularly costated;
    spire short, with rounded, dome-like whorls; aperture wide,
    emarginated; outer lip thickened, reflected, composing the last costa
    or rib; inner lip polished, spread over part of the body whorl,
    terminating in a point.--_Obs._ This beautiful genus of shells is so
    clearly defined by the regular, longitudinal ribs that adorn the
    external surface, suggesting the idea of a stringed instrument, that
    there is no danger of confounding it with any other. H. multicostata,
    (Buccinum costatum, Linn.) and H. ventricosa, are among the most
    elegant of the testaceous productions of the sea both in form and
    colouring; the former is rare. The recent species are not numerous,
    they inhabit the Indian Ocean. A fossil species occurs at Grignon, near
    Paris. Fig. 419, H. ventricosa.

    HARPAX. Parkinson. Part of PLICATULA, Auct.

    HARPULA. Sw. A group of shells separated from VOLUTA, Auct. thus
    described, "shell generally tuberculated or longitudinally ribbed; apex
    of the spire papillary, smooth, and in general distorted; pillar with
    numerous distinct plaits; the upper, small and slender, the lower,
    thickest and shortest."--_Type_, H. Vexillum. (Voluta, Auct.)

    HAUSTATOR. Montf. A genus proposed to include those species of
    TURRITELLA, Auct. which have angulated whorls.

    HAUSTELLARIA. Sw. A sub-genus of Murex, consisting of species with long
    canal and no spines. Murex Haustellum, fig. 396.

    HAUSTRUM. Humph. PURPURA, Lamarck.

    HELCION. Montfort. A genus composed of species of Patella, which have
    the apex distinctly and prominently bent forwards. _Ex._ P. pellucida,
    fig. 230.

    HELENIS. Montf. A genus of microscopic Foraminifera.

    HELICELLA. Fer. One of the sub-genera into which De Ferussac has
    divided the genus Helix, consisting of depressed species with large
    umbilicus, such as Helix Algira, fig. 279. Gonites Montf.

    HELICIFORM. Shaped like shells of the genus Helix.

    HELICIGONA. One of De Ferussac's sub-genera of the genus HELIX,
    consisting of angulated species, such as Carocolla Lamarckii, fig. 277.

    HELICINA. Lam. _Fam._ Colimacea, Lam. Ellipsostomata, Bl.--_Descr._
    Globose, compressed, or angulated, generally light and thin; aperture
    trigonal or semilunar; outer lip thickened and generally more or less
    reflected; inner lip spread over the body whorl, frequently callous
    near the columella, which is short, and terminates in a notch, angle,
    or slight callosity.--_Obs._ This genus of land shells, distinguished
    from the genus Helix, by having an operculum and a thickened columellar
    lip, differs also from Cyclostoma in having the aperture semicircular
    or angular, the peritreme discontinuous and the operculum concentric.
    These shells are generally small in size, and simple in form. Lamarck
    describes only three or four species. Mr. Gray described some others in
    the Zoological Journal, and in a work shortly to be published by the
    author, a monograph of the genus will contain descriptions and figures
    of at least 60 distinct species; some of which have been lately brought
    to this country by Mr. Cuming from the Philippine Islands. They mostly
    belong to tropical climates.

    HELICITES. Bl. Part of the genus NUMMULITES, Lam. ROTALITES and EGEON,
    Montf.

    HELICOGENA. Fer. A sub-genus of Helix, consisting of species, which,
    like the common garden snail, fig. 268, are globose and simple in form.

    HELICOLIMAX. Fer. VITRINA, Drap. H. Pellucida, fig. 263.

    HELICOPHANTA. Fer. A sub-genus of Helix, consisting of ear-shaped
    species with large open apertures.

    HELICOSTYLA. Fer. A sub-genus of Helix, consisting of species with
    numerous whorls, as H. Epistylium, fig. 281.

    HELISOMA. Sw. A sub-genus of Planorbis. Sw. p. 337.

    HELIX. Auct. _Fam._ Colimacea, Lam.--_Descr._ Orbicular, light,
    generally globular; spire short, last whorl ventricose, aperture
    oblique, peritreme reflected, interrupted by the most prominent part of
    the body whorl; columella confluent with the outer lip, and contiguous
    to the axis of the shell. No operculum; a thin epidermis.--_Obs._ The
    land shells composing this genus are found in all parts of the world;
    the common snail, H. Aspersa, is well known as a destructive animal in
    our gardens. The genera Helix, Achatina, Bulinus, Clausilia, Anostoma,
    &c., have been united under one generic name by De Ferussac, and again
    divided under the following sub-generic names, each of which we shall
    illustrate by a figure. GENUS HELIX: _Sub-genus_ 1, _Helicophanta_,
    consisting of species with large apertures, like Vitrina; Helix
    brevipes. _S. gen. 2_, _Cochlohydra_, Succinea Amphibia, Drap. _S. gen.
    3_, _Helicogena_, consisting of the common species with the last whorl
    large; Helix Hæmastoma, H. Contusa, (Streptaxis, Gray,) H. Aspersa. _S.
    gen. 4_, _Helicodonta_, consisting of species with teeth or folds on
    the columella; Polydonta, Montf. Anostoma, Helix Nux-denticulata. _S.
    gen. 5_, _Helicigona_, Carocolla, Geotrochus. _S. gen. 6_, _Helicella_,
    consisting of depressed species with a large umbilicus; H. Citrina
    (Naninia, Gray.) _S. gen. 7_, _Helicostyla_, consisting of species with
    a simple aperture, like the Helicogenæ, but with the whorls increasing
    very gradually; H. epistylium. _S. gen. 8_, _Cochlostyla_, Bulinus. _S.
    gen. 9_, _Cochlitoma_, Achatina. _S. gen. 10_, _Cochlicopa_, Polyphemus
    Glans. _S. gen. 11_, _Cochlicella_, Bulinus decollatus. _S. gen. 12_,
    _Cochlogena_, Azeca tridens. _S. gen. 13_, _Cochlodonta_, Pupa Uva. _S.
    gen. 14_, _Cochlodina_, Clausilia macascarensis, Balea fragilis. The
    last three sub-genera are included in the genus Odostomia of Fleming.
    We give an example of each of these sub-divisions, for the sake of
    presenting the reader with the principal variations to which the genus
    is subject. The established genera will be characterized in their
    places. Fig. 254 to 281.

    HELIXARION. Fer. VITRINA, Drap. Differing from Helicolimax in the
    structure of the animal. Fig. 262.

    HEMICARDIUM. Cuv. ([Greek: hêmisus], _hemisus_, half, [Greek: Kardia],
    _cardia_, heart.) CARDIUM Hemicardium, fig. 123**, and several similar
    species.

    HEMICYCLA. Sw. A sub-genus of Helix.

    HEMICYCLONOSTA--see CARDILIA.

    HEMICYCLOSTOMATA. Bl. The fourth family of Asiphonibranchiata, Bl.
    described as "more or less globular, thick, flattened on the under
    side; spire very short; aperture large, semilunar, entire; its outer
    edge hollowed; its inner or columellar edge straight, sharp and
    septiform." This family answers to the genus _Nerita_ of Linnæus, and
    to the family Neritacea of Lamarck. It contains the genera Natica,
    Nerita, Neritina, and Navicella.

    HEMIMACTRA. Sw. A sub-genus of Mactra, thus described: "General form of
    _Mactra_; but the cardinal teeth entirely wanting; cartilage internal,
    central, in a large triangular cavity; lateral teeth 2/1, distinct,
    lateral, striated: connected to the _Glycimeri_. H. gigantea, _Lam._ v.
    472. No. 1. grandis, _Sw._ Sp. Nov." Sw. p. 369.

    HEMIMITRA. Sw. A sub-genus of Paludomus, Sw. (Melanianæ.)

    HEMIODON. Sw. A sub-genus of Anodon, described as having "Tubercles or
    undulations on the hinge margin. H. undulatus, purpurascens and
    areolata."

    HEMISINUS. Sw. A sub-genus of Melania, thus described: "General shape
    of _Melania_; but the base of the aperture is contracted and
    emarginate; outer lip crenated. H. lineolata, Griff. Cuv. xii. pl. 13.
    fig. 4."

    HEMITOMA. Sw. A sub-genus of Emarginula, thus described: "Patelliform;
    the fissure not cut through the shell, but merely forming an internal
    groove. H. tricostata, _Sw._ Sow. Gen. fig. 6."

    HEMITROCHUS. Sw. A sub-genus of Geotrochus, Sw. H. hæmastoma. Sw. p.
    331.

    HEPTALASMIS. Leach. ([Greek: Hêpta], _hepta_, seven; [Greek: elasma],
    _elasma_, plate) A small shell resembling Pentelasmis, from which it
    differs in the number of valves, being composed of seven valves
    according to Leach, and of eight according to Gray, who counts the
    dorsal valve, which is jointed, as _two_, and names his genus
    Octolasmis. Fig. 41, H. Warwickii.

    HERCOLES. Montf. A microscope shell, appearing from De Montfort's
    figure to resemble TROCHUS _Imperialis_ in shape.

    HERION. Montf. LENTICULINA, Bl. Microscopic.

    HERMAPHRODITA. Bl. The third sub-class of Paracephalophora, Bl. divided
    into, Sect. 1, _symmetrical_, containing the orders Cirrobranchiata and
    Cervicobranchiata; Sect. 2, _non-symmetrical_, order, Scutibranchiata.

    HERMES. Montf. A genus composed of CONUS _Nussatella_, Auct. and other
    elongated, cylindrical, striated species. Fig. 460.

    HETEROBRANCHIATA. Bl. The fourth order of the class Acephalophora, Bl.
    containing no testaceous mollusca.

    HETEROPODA. Lam. The fifth order of the class Mollusca, Lam. This order
    contains but one genus of shells, viz. Carinaria, fig. 488.

    HETEROSTEGINA. D'Orb. A genus of microscopic Foraminifera.

    HIATELLA. Daud. Fam. Lithophagidæ, Lam. A genus composed of species of
    Saxicava, Auct. which have sharp, angulated, posterior ridges, a
    circumstance which occurs to many species in a young state, which
    afterwards become rounded off. Fig. 95, Hiatella biaperta.

    HIATULA. Sw. A genus proposed to include those species of Oliva, Auct.
    which have widened apertures. _Ex._ O. Subulata, fig. 458.

    HIBOLITHES. Montf. A genus composed of species of Belemnites, Auct.
    which are swelled towards the apex, and contracted near the centre. B.
    Hastatus, Auct. fig. 468.

    HIMANTOPODA. Schum. MALLEUS, Auct.

    HINGE. The edge of the bivalve shells near the umbones, including the
    teeth and ligament.

    HINNITES. Defr. A generic name proposed for PECTEN PUSIO, Auct.
    remarkable for the irregularity of the outer surface, which would
    almost lead to the belief of its being an attached shell. Fig. 173, H.
    Pusio.

    HIPPAGUS. Lea. (_Horse boat._) A minute fossil shell, resembling
    Isocardia in form, but destitute of hinge teeth. H. Isocardioides, fig.
    128.

    HIPPOCHRENES. Montf. Species of ROSTELLARIA, Auct. with the outer lip
    spread. Fig. 403. R. Columbaria.

    HIPPONYX. ([Greek: Hippos], _hippos_, horse; [Greek: onux], _onyx_,
    nail or hoof.) _Fam._ Rudistes, Lam.--_Descr._ Inequivalve,
    sub-equilateral, rather irregular, destitute of ligament and hinge
    teeth; lower valve attached, flat, sub-orbicular, with a muscular
    impression, composed of two lunulate portions, meeting at one
    extremity, and presenting the form of a horse-shoe; upper valve
    conical, with the apex inclined backwards, and the muscular impression
    marginal.--_Obs._ The earlier naturalists having only met with the
    upper valve of these shells, placed them among the patelliform
    univalves; to some of which, particularly Pileopsis, they bear a very
    strong resemblance. The species of Hipponyx are numerous, and till
    lately only known in a fossil state. The recent species belong to
    tropical climates: the fossil species are found in the tertiary beds.
    Fig. 199, H. Cornucopia.

    HIPPOPODIUM. Conybeare. _Fam._ Cardiacea, Lam.--_Descr._ Equivalve,
    obliquely transverse, heavy, deep, inequilateral, umbones incurved;
    ventral margin sinuated, so as to give a bilobed appearance to the
    shell; hinge incrassated, with one rugged oblique tooth.--_Obs._ These
    fossils are found in the upper beds of Lias. Fig. 129, H. Ponderosum.

    HIPPOPUS. Lam. ([Greek: Hippos], hippus; [Greek: pous], _pous_, foot.)
    _Fam._ Tridacnacea, Lam.--_Descr._ Equivalve, inequilateral, regular,
    subquadrate; lunule closed, flat, with crenulated edges; ventral margin
    deeply undulated; external surface fluted, with radiating ribs, which
    are transversely fringed with rows of tubular spines; hinge margin
    thick, with two long, compressed posterior lateral teeth in one valve,
    three in the other; ligament marginal, external.--_Obs._ The shell thus
    described is rightly separated from Tridacna, on account of the
    anterior dorsal margins being closed; whereas in Tridacna there is a
    wide hiatus. Only one species of this genus is known, which receives
    its name from its resemblance in form to a horse's foot, when held with
    the flat anterior dorsal margin downwards. Few shells are found to
    concentrate so many beauties as the Hippopus Maculatus, commonly called
    the Bear's-paw-clam; the delicate whiteness of the interior, the
    undulating edge, the radiated fluted columns, adorned at intervals by
    crisped fringes, and the richness of the variegated colouring, are such
    as to secure the admiration of the most superficial observer. From the
    Indian Archipelago. Fig. 156, H. Maculatus.

    HIPPURITES. Montf. _Fam._ Orthocerata, Lam. Rudistes, Bl.--_Descr._
    Tabular, rude, irregular, attached; lower valve cylindrical, more or
    less lengthened, apparently divided into sections by septa (considered
    by some authors as merely projecting layers of growth) having one or
    two lateral tubes within; upper valve round, flat, fixed on the
    aperture of the tubular valve like an operculum.--_Obs._ This genus is
    known only in a fossil state, and but very imperfectly. Lamarck places
    it among his chambered Cephalopoda, &c. De Blainville, considering it a
    true Bivalve, enumerates it among his Rudistes. Cretaceous group. Fig.
    198, H. Cornucopia.

    HORTOLUS. Montf. SPIROLINA, Lam. Microscopic.

    HYALÆA. Auct. (_Hyalus_, glass.) _Fam._ Pteropoda, Lam. Thecosomata,
    Bl.--_Descr._ Globose, glassy, transparent, with a triangular opening
    at the upper part where the dorsal portion advances beyond the ventral;
    ventral portion vaulted; dorsal more flat; lower extremity
    tridentate.--_Obs._ The singular structures composing this genus were
    formerly taken for bivalves, and named Anomia Tricuspidata, &c. They
    are now known to belong to the class of molluscous animals, called
    Pteropoda, from the wing-shaped organs of locomotion. A species of
    Hyalæa occurs in Sicily in a fossil state. Recent species are found in
    the Mediterranean, Atlantic, and Indian Oceans. Fig. 226, H.
    Tridentata.

    HYALINA, Studer. VITRINA, Drap.

    HYALINE. (_Hyalus_, glass.) Glassy, thin, transparent--_Ex._ Carinaria
    Mediterranea, fig. 488.

    HYDROBRANCHIATA. Bl. The first section of the order Gasteropoda, Lam.
    containing Molluscs which breathe water only; divided into the families
    Tritoniana, Phyllidiana, Semi-phyllidiana, Calyptracea, Bullæana, and
    Aplysiana.

    HYGROMANES. Fer. A sub-division of Helix, containing H. limbata, Auct.
    &c. Gray's Turton, p. 143.

    HYRIA. Lam. A genus composed of species of Nayades, distinguished by
    their alated dorsal margins, and lamellated lateral teeth. South
    America. HYRIA corrugata, fig. 143, Hyria Syrmatophora, fig. 144.

    HYRIDELLA. Sw. A genus of "Hyrianæ," Sw. described as differing from
    HYRIA, Auct. in having a cardinal as well as a lateral tooth in each
    valve. Sw. p. 380.

    HISTRIX. Humph. RICINULA, Auct.

    JANERA. Schum. A genus composed of species of Pecten, Auct. having
    oblique plicæ or calli on each side of the ligamentary pit. _Ex._ P.
    plica, fig. 172. Decadopecten, Rüppell.

    JANTHINA. Auct. (_Janthum_, a violet.) _Fam._ Neritacea, Lam.
    Oxystomata, Bl.--_Descr._ Sub-globose, thin, fragile; spire short,
    consisting of few whorls; aperture angulated, at the anterior junction
    of the inner and outer lips; columella tortuous, contiguous to the
    axis; outer lip thin, sinuated in the centre.--_Obs._ The shells
    composing this genus are celebrated for their beautiful purple colour.
    The animal possesses a small vesicular process, which keeps it floating
    on the surface of the water; it exudes a purple secretion when
    irritated. It is occasionally floated on to the shores of most
    temperate and tropical countries. Fig. 333, J. Fragilis.

    JATARONUS. Adanson. CHAMA, Auct.

    IBERUS. Montf. CAROCOLLA, Lam.

    IBLA. Leach. _Fam._ Pedunculated Cirripedes, Lam.--_Descr._ Four
    valves, posterior pair elongated, anterior pair short, triangular;
    pedicle cylindrical, contracted at the base, hairy.--_Obs._ I.
    Cuveriana (fig. 40) is brought from Kangaroo Island.

    ICTHYOSARCOLITES. Desmarest. _Fam._ Ammonacea, Lam.--_Descr._
    Chambered, slightly arcuate, laterally compressed; septa simple,
    leaving triangular articulations imbricated like the thick muscles of a
    fish.

    JESITES. Montf. A minute fossil resembling GALEOLARIA.

    ILOTES. Montf. ORBICULINA, Bl. A genus of microscopic Foraminifera.

    IMBRICARIA. Schum. CONOHELIX, Sw.

    IMBRICATED. (_Imbrex_, a tile.) A shell is said to be imbricated when
    the superficial laminæ are arranged over each other in the manner of
    tiles.

    IMPERATOR. Montf. A genus composed of species of the genus TROCHUS,
    Auct. with whorls angulated and stellated, having an umbilicus. _Ex._
    T. Imperialis. Some of the shells named Imperator in the British Museum
    belong to the genus Calcar, Montf. having no umbilicus.

    IMPRESSION. See MUSCULAR IMPRESSION.

    INCRASSATED. (_Crassus_, thick.) Thickened, as the hinge of Glycimeris,
    fig. 67.

    INCURVED. Turned inwards or bent forwards. Applied to symmetrical
    shells, when the point of the apex turns towards the anterior
    extremity, as in Patella. The apex of a shell is said to be incurved
    when it is bent inwards, but not sufficiently so to be described as
    spiral. _Ex._ Ammonoceras, Lam. fig. 477.

    INDENTED. (_In_, in; _dens_, a tooth.) Exactly the reverse of DENTATED;
    meaning a series of small cavities, such as might be produced by the
    entrance of teeth. The cast of a dentated surface would be indented.

    INEQUILATERAL. (_Æquus_, equal; _latus_, a side.) A term applied to a
    bivalve shell when its extent on one side of the umbones is greater
    than that on the other. When the sides are nearly equal, the term
    _sub-equilateral_ is used.

    INEQUIVALVE. (_in_; _æquus_, equal; _valva_, valve.) The two principal
    valves differing from each other in diameter or convexity.

    INFERIOR VALVE is that which is attached to sub-marine bodies. Only
    applied to attached bivalves.

    INFEROBRANCHIATA. Bl. The fourth family of the second section of
    Paracephalophora Monoica, Bl. containing no testaceous mollusca.

    INFLATED. Swelled, as Bulla, fig. 250, 252. This term can only be
    applied to rotund shells of a light, thin texture. In other cases we
    should use the word VENTRICOSE.

    INFLECTED. Turned inwards. This term is applied to the outer lip of a
    spiral shell when it turns towards the body whorl. This is the case in
    Cypræa, fig. 446. See REFLECTED.

    INFUNDIBULUM. Montf. (_A funnel._) A genus formed of those species of
    CALYPTRÆA, Lam. which, having a spiral septum, so nearly resemble
    Trochus that some authors have placed them in that genus. One species
    named Patella Trochiformis. Recent from South America, fossil from the
    tertiary beds. Fig. 237, 238, Calyptræa (Infundibulum) Pileus.

    INNER LIP. That edge of the aperture of an univalve shell which is near
    to the imaginary axis, as distinguished from the outer lip, or that
    which is on the opposite side.

    INOCERAMUS. Sow. _Fam._ Malleacea, Lam. Margaritacea, Bl.--_Descr._
    Thick, inequivalve, sub-equilateral, triangular, deep, with the umbones
    incurved; hinge formed of a series of transverse grooves.--_Obs._ The
    larger valves of these fossil shells resemble the larger valve of
    Gryphæa; but the hinge is quite distinct. The species described in
    Mineral Conchology are found in the blue marl, at Folkstone, and in the
    chalk. I. Lamarckii, (Catillus, Brong.) fig. 167.

    INTERNAL CAST. The mould of a fossil shell, composed of matter which
    entered the shell in a soft state, and has subsequently hardened, when,
    the shell dropping off, the hardened substance which filled it is left
    to represent its internal form.

    INTERNAL LIGAMENT. A term used by some conchological writers signifying
    that the ligament of a bivalve shell is placed within the closed part
    of the hinge, so as not to be seen when the valves are shut. But the
    substance, formerly called the internal ligament, is now distinguished
    from the true ligament both in structure and use; and is now more
    properly called the cartilage, so that when the ligament is said to be
    internal, it must be understood that the internal cartilage is
    unaccompanied by any ligament properly so called, and when a shell is
    described as having two ligaments, as in the case of Amphidesma, it
    means that the two substances are so far removed from each other in the
    hinge that they are no longer confounded together.

    INTERNAL SHELL is one which is enclosed in the soft parts of the
    animal, as a bone is enclosed in the flesh of a human body. The Limax,
    or common garden slug, which has a testaceous shield beneath its
    mantle, is an instance of this.

    IO. Lea. A genus composed of several species of fresh-water shells
    which are considered as differing from Melaniæ in having the anterior
    termination of the aperture produced into a point in some degree
    resembling the caudal canals of shells belonging to the family of
    Canalifera, which are marine. Io fusiformis and spinosus are described
    and figured in Lea's work on the genus Unio.

    JODAMIA. Defr. A genus resembling Birostrites, except that in Jodamia
    one valve overwraps the other, while in Birostrites the circumference
    of the valves is equal.

    IPHIGENIA. Gray. A sub-genus of Clausilia, C. biplicata, &c. Auct.
    Gray's Turton, p. 214.

    IRIDEA. Sw. A genus of "Hyrianæ," Sw. thus described:--"Oblong ovate;
    bosses small, depressed, sulcated; inner cardinal tooth placed beneath
    the outer. I. granosa, _Lam._ En. Méth. 248. fig. 9."

    IRIDINA. Auct. A genus belonging to the Nayades, and resembling the
    ANODONTÆ, Auct. but its peculiar characteristic is that the hinge
    lamina is tuberculated or crenulated in its whole length. Sowerby
    unites all the genera of the family into the genus UNIO. Fig. 150, I.
    Elongata.

    IRREGULAR SHELLS, are those which, being attached to, or imbedded in
    other marine bodies, have no constant form, but are modified in shape
    according to the substances to which they are fixed, as the Chamacea,
    fig. 153 to 155.

    IRUS. Oken. Comprehending PANDORA, PETRICOLA, SAXICAVA, &c.

    ISOCARDIA. Lam. ([Greek: Isos], _isos_, similar; [Greek: Kardia],
    _cardia_, heart.) _Fam._ Cardiacea, Lam. Chamacea, Bl.--_Descr._
    Cordiform, regular, equivalve, ventricose, with distant, diverging,
    involute, free umbones; hinge with two compressed cardinal, and one
    distant, compressed lateral teeth in each valve; ligament external,
    bifid, diverging in the direction of the umbones.--_Obs._ The shells
    composing this genus are remarkable for the beautiful curvature of the
    diverging umbones. European and Chinese Seas. Fig. 126, I. Moltkiana.

    KEEL. A flattened ridge, resembling the keel of a ship. As that on the
    back of Carinaria vitrea, fig. 488, and those on the whorls of some
    spiral shells. A shell characterized by a keel or keels is said to be
    carinated.

    KELLIA. Turton, MYA Suborbicularis, Montague.

    LABIS. Oken. MONODONTA, Lam.

    LABIUM, or inner lip,--is used to express that side of the aperture
    which is nearest to the axis and generally contiguous to the body
    whorl. The lower part of this, when sufficiently distinct from that
    part which overwraps the body whorl, is called the Columella.

    LABRUM, or outer lip,--is the edge of the aperture at the greatest
    distance from the axis.

    LACINEA. Humph. CHAMA, Lam.

    LACUNA. Turt. _Fam._ Turbinacea, Lam.--_Descr._ Globose, thin, covered
    with a smooth epidermis; spire short, consisting of few rapidly
    increasing whorls; aperture semilunar, rounded at the extremities;
    columella oblique, reflected over part of the umbilicus; umbilicus
    forming a lengthened area behind the columella. Northern shores. Fig
    364, L. Pallidula.

    LAGENULA. Montf. A genus of microscopic Foraminifera.

    LAMELLATED. (_Lamella_, a thin plate.) When the layers of which a shell
    is composed, instead of being compacted into a solid mass, are
    separated, overlying each other in the manner of tiles, with the edges
    prominent, the structure is said to be lamellated or foliaceous.

    LAMELLIBRANCHIATA. Bl. The third order of the class Acephalophora, Bl.
    consisting of bivalve shells, divided into the families Ostracea,
    Subostracea, Margaritacea, Mytilacea, Polydontes, Submytilacea,
    Chamacea, Conchacea, Pylorides, Adesmacea.

    LAMELLIPEDES. Lam. (_Lamella_, a thin plate, _pes_, a foot.) The third
    section of the order Conchifera Dimyaria, containing bivalves, with the
    foot of the animal broad and thin; divided into the families Conchacea,
    Cardiacea, Arcacea, Trigonacea, Nayades. Fig. 111. to 152.

    LAMPAS. Montf. LENTICULINA, Bl. A genus of microscopic Foraminifera.

    LAMPRODOMA. Sw. A genus of "Olivinæ," Sw. thus described:--"Mitriform;
    spire produced, conic; resembling MITRELLA in shape, but the suture is
    channelled; the aperture effuse at the base, contracted above; lower
    half of the pillar with 6 to 7 plaits. Volutella, Zool. Ill. ii.
    series, pl. 40. f. 1. (_fig. 86._ )" Sw. p. 321.

    LAMPROSCAPHA. Sw. A sub-genus of "Anodontinæ," Sw. thus
    described:--"Shell not winged, elongate, pod-shaped; teeth none; bosses
    near the anterior extremity. Tropical America only? L. ? elongata.
    _Sw._ Zool. Ill. i. 176. ensiforme, _Spix._ Braz. Test. siliquosa.
    Braz. Test. pygmæa. Ib." Sw. p. 381.

    LAMPROSTOMA. Sw. A sub-genus of Canthorbis (Trochus), described at p.
    350, Lardn. Cyclop. Malac.

    LAMPUS. Humph. TEREBRATULA, Lam.

    LANCEOLATE. Lengthened like a lance.

    LANISTES. Montf. Reversed species of AMPULLARIA, fig. 319.

    LAPLYSIA. See APLYSIA.

    LAPLYSIACEA. Lam. (properly Aplysiacea) A family belonging to the first
    section of the order Gasteropoda, Lam. containing the genera Aplysia
    and Dolabella. Fig. 254, 255.

    LARVA. Humph. FISSURELLA, Lam.

    LATERAL. (_Latus_, a side.) The lateral teeth are those which, taking
    their rise near the umbones, proceed to some distance towards the sides
    of the shell; as distinguished from the cardinal teeth, which receive
    their full developement close to the umbones. Lateral muscular
    impressions are those which are placed at a distance from each other,
    on the opposite sides of the shell.

    LATIAXIS. Sw. A genus of "Eburninæ," Sw. corresponding with the genus
    Trichotropis. Sow. (Sw. Malac. p. 306.)

    LATIRUS. Montf. A genus composed of species of FUSUS, Auct. which have
    an umbilicus and are turriculated.

    LAURIA. Gray. A sub-genus of PUPA, containing P. umbilicata, &c.
    (Gray's Turton, p. 193.)

    LEGUMINARIA. Schum. A genus composed of species of SOLEN, Auct. which
    have an internal longitudinal bar or rib. Fig. 61. S. Radiatus, Lam.

    LEILA. Gray? Described as having the hinge edge smooth like Iridina,
    but having a "sharp siphonal inflexion." (Syn. B. M. p. 142.)

    LEIODOMUS. Sw. A genus of "Buccininæ," Sw. consisting of Terebra
    vittata and other similar species. This genus corresponds with Bullia,
    Gray.

    LEIOSTOMA. Sw. A genus of "Fusinæ," Sw. thus described, "Equally
    fusiform," (with Fusus) "but ventricose in the middle; shell entirely
    smooth, almost polished; inner lip thickened, and vitreous; base of the
    pillar very straight. Fossil only. (_fig. 75._) L. bulbiformis. En.
    Méth. 428. f. 1."

    LEMBULUS. Leach. A genus composed of oval species of NUCULA, resembling
    N. margaritacea, fig. 137.

    LENDIX. Humph. PUPA, Lam.

    LENGTH. See MEASUREMENT.

    LENTICULAR. (_Lens._) Of a circular, convex form, as Pectunculus, fig.
    134.

    LENTICULINA. Lam. A genus of microscopic Foraminifera.--_Descr._
    Lenticular, sub-discoidal, compressed, convolute, symmetrical; aperture
    notched; chambers few in number; visible on the exterior, radiating
    from the centre of the disk.

    LEPADICEA. Bl. The first family of the class Nemantopoda, Bl. This
    family consists of the same animals which constitute the Pedunculated
    Cirripedes of Lamarck, and part of the genus Lepas in the system of
    Linnæus. It contains the genera Gymnolepas, Pentalepas, Polylepas and
    Litholepas.

    LEPAS. ([Greek: Lepas], _lepas_, a rock.) The Linnæan name Lepas
    contains all the Cirripedes or Multivalves, the different kinds of
    which are not distinguished in the accounts given by early writers of
    the habits of the animals. (Fig. 14 to 43.) It was formerly applied to
    the Limpets or Patella. In fact, the ancient definition was "Concha
    petræ adhærens," and would apply to any shells attached to rocks.

    LEPTÆNA. Dalman. A genus belonging to the Brachiopoda; and thus
    described:--"Hinge compressed, rectilinear, frequently exceeding the
    width of the shell." It forms part of the genus Producta, Sow. Fig.
    206, L. depressa.

    LEPTOCONCHUS. Rüppell. ([Greek: Leptos], _leptus_, thin; [Greek:
    Konchos], _conchos_, shell.) This shell resembles a young MAGILUS in
    general appearance, although the animal is said to differ. In the young
    Magilus also, the inner lip is reflected over the body whorl, which is
    not the case in Leptoconchus. Red Sea. Fig. 11.

    LEPTOCONUS. Sw. A sub-genus of Conus, consisting of Conus grandis,
    amadis, duplicatus, Australis, &c. Sw. p. 312.

    LEPTOLIMNEA. Sw. A sub-genus of Limnea, described as being nearly
    cylindrical. Limnea elongata, Sow. Gen. fig. 6.

    LEPTON. Turton. SOLEN Squamosus, Montague, and other species described
    as "flat, nearly orbicular, equivalve, inequilateral, a little open at
    the sides. Hinge of one valve with a single tooth, and a transverse
    linear lateral one on each side; of the other valve, with a cavity in
    the middle and a transverse deeply cloven lateral tooth each side, the
    segments of which divaricate from the beak." To represent this genus we
    have figured L. Squamosum in the plates, fig. 62. British.

    LEPTOSPIRA. Sw. A sub-genus of Bulinus, thus described: "Spire
    excessively long, sub-cylindrical; body whorl largest; outer lip
    thickened; aperture oval; no teeth, striata, _Sw._ Chem. 135. f. 1226.
    signata _Sw._" Sw. p. 335.

    LEUCOSTOMA. Sw. A genus of "Achatina," Sw. described as resembling
    Achatinella, but having a "thick pad" at the top of the "upper lip,"
    and another over the base. L. variegata, Sw. Lardn. Cyclop. Malac. fig.
    24. p. 172.

    LEUCOTUS. Sw. A sub-genus of Natica, described as intermediate between
    Sigaretus and Lacuna. SIGARETUS _cancellatus_, Lam. (Sw. Malac. p.
    346.)

    LICIUM. Humph. OVULA, Lam. (Ovulum.)

    LIGAMENT. (From _Ligo_, to bind.) The true ligament is always external,
    and serves the purpose of binding the two valves of a shell together
    externally by the posterior dorsal margins. There is another substance,
    called by Gray the _Cartilage_, which is elastic and of a condensed
    fibrous structure, placed within the ligament, either close to it, or
    at a more interior part of the shell; it is sometimes contained in a
    pit, formed for its reception, in the centre of the hinge. This
    substance, being elastic, keeps the valves open, unless drawn together
    by the counteracting force of the adductor muscles. When conchologists
    speak of a shell as having the ligament external, the real meaning is
    that these two substances are so close together as in appearance to
    constitute one body placed outside the shell so as to be seen when the
    valves are closed. When two ligaments are spoken of, as in Amphidesma,
    the meaning is that the cartilage occupies a separate place on the
    hinge.

    LIGAMENTIFEROUS. (_Ligamentum_, a ligament, _fero_, to bear.) Having or
    containing the ligament, as the cardinal pit in Mya, fig. 71.

    LIGULA. Leach. A genus containing the more rounded and less gaping
    species of LUTRARIA, Auct. Fig. 77, Lutraria Papyracea.

    LIGULATE. (_Ligula_, a slip, a shoe-latchet.) Thin, slender, like a
    slip, or neck of any thing, as the anterior muscular impression of
    Lucina, fig. 104.

    LIGUMIA. Sw. A sub-genus of Unio, thus described:--"Very long and
    pod-shaped; bosses depressed; cardinal teeth moderate. S. recta. Lam.
    vi. 1. p. 74." Sw. p. 378.

    LIGUUS. Montf. A genus containing species of ACHATINA, Auct. which have
    rounded apertures and lengthened spires, differing from his POLYPHEMI,
    which have lengthened apertures. A. virginea, Auct. fig. 286, is the
    type of this genus.

    LIMA. Brug. (_Lima_, a file.) _Fam._ Pectinides, Lam. Subostracea,
    Bl.--_Descr._ Equivalve, inequilateral, compressed,
    oblique-auriculated, oval, radiately ribbed or striated, imbricated,
    covered with a light brown epidermis; hinge with a triangular disc
    between the umbones, divided in the centre by a triangular ligamentary
    pit without teeth; muscular impression one, sublateral,
    sub-orbicular.--_Obs._ The shells thus described are marine, two or
    three species being found on our coasts, and fossil species occurring
    in Lias, inferior Oolite, Calcaire-grossiér, &c. They differ from
    Pecten in having a wide hiatus for the passage of a byssus, by which
    they are occasionally attached, and also in the triangular disc, which
    separates the umbones. The animal makes use of the valves of his shell
    as natatory organs, working them like fins or paddles, and by this
    means proceeding at a rapid rate through the waters. L. Squamosa, fig.
    174.

    LIMACINA. Cuv. (_Limax_, a snail.) _Fam._ Pteropoda, Lam.--_Descr._
    Papyraceous, fragile, planorbicular, sub-carinated, obliquely
    convolute; spiral side rather prominent, the other side umbilicated;
    aperture large, entire, not modified, peristome sharp.--_Obs._ This is
    SPIRATELLA, Bl. The shell figured as Limacina in Sowerby's Genera,
    under "pteropoda," is an _Atlanta_. Our representation of Spiratella
    Limacinea, fig. 224. is copied from Blainville.

    LIMACINEA. Lam. A family of the order Gasteropoda, Lam. including the
    following

        1. CRYPTELLA. Spire mammillated; a septum. Fig. 256.

        2. PARMACELLA. Flat, haliotoid, spiral. Fig. 257, 258.

        3. TESTACELLUS. Sub-spiral. Fig. 261.

        4. LIMAX. Incomplete. Fig. 259.

        5. PLECTROPHORUS. Conical. Fig. 260.

        6. VITRINA. Heliciform, hyaline. Fig. 262, 263.

    LIMACINEA. Bl. The third family of the order Pulmobranchiata, Bl.
    Described as containing shells very variable in form, most frequently
    inclining to globular or oval; the apex always obtuse; aperture
    variable, but never emarginated. All the Limacinea are phytophagous and
    terrestrial. This family answers to the genus Helix of Linnæus and to
    the Colimacea of Lamarck, leaving out the Auriculacea. It contains the
    genera Succinea, Bulinus, Achatina, Clausilia, Pupa, Partula, Helix,
    Vitrina, Testacella, Limacella, Limax.

    LIMAX. _Lam._ Limacinea, Lam. and Bl.--_Descr._ Internal irregular,
    sub-quadrate, scutiform, crystalline; apex rounded, indistinct;
    epidermis, light brown, thin, extending beyond the margin.--_Obs._ The
    shell is placed under the scutellum of the common garden slug. Fig. 25,
    L. Antiquorum.

    LIMNACEA. Bl. The first family of the order Pulmobranchiata, Bl. The
    shells of this family are described as thin, with the outer lip always
    sharp. It contains the genera Limnea, Physa, Planorbis.

    LIMNEANA. Lam. A family of the order Trachelipoda, Lam. containing the
    following genera:--

        1. LIMNÆA. Spire produced; including _Physa_. Fig. 308 to 310.

        2. PLANORBIS. Spire orbicular; including _Planaria_. Fig. 311, 312.

    LIMNEA. Lam. ([Greek: Limnas], _limnas_, lacustrine.) _Fam._ Limnacea,
    Lam. and Bl.--_Descr._ Oblong, light, thin; spire variable in length,
    acute; last whorl large, aperture large, longitudinal, entire; inner
    lip spread over a portion of the last whorl; columella forming an
    oblique fold; outer lip rounded at each extremity, thin.--_Obs._ These
    light horn-coloured shells are common in standing pools, ponds and
    ditches, in various parts of Europe. They resemble the Amber shell
    (Succinea) in shape, but the animal of the latter is amphibious, and
    the shell of a bright amber colour. L. Stagnalis, fig. 308. L.
    auricularia, fig. 309. (RADIX, Montf.) The reversed species have been
    separated under the name Physa, fig. 310. Other generic names have been
    given to other species.

    LINES OF GROWTH. The concentric striæ or lines formed by the edges of
    the successive layers of shelly matter deposited by the animal by which
    it increases the shell. The outer edge of the aperture is always the
    last line of growth.

    LINGUIFORM. (_Lingua_, tongue; _forma_, form.) Tongue-shaped.

    LINGULA. Lam. (Dim. from _lingua_, tongue.) _Fam._ Brachiopoda, Lam.
    Palliobranchiata, Bl.--_Descr._ Equivalve, oblong, depressed, thin,
    equilateral, gaping and pointed at the umbones, gaping and truncate or
    trilobate at the opposite extremities, attached by a fleshy pedicule
    fixed to the umbones.--_Obs._ This is the only bivalve shell which is
    pedunculated, in which respect it constitutes a singular anomaly. The
    ancient writers, seeing the valves separate, placed it in their systems
    under the name Patella Unguis. There are several recent species found
    in the Moluccas, and some fossils in sandy indurated marl, and in
    alluvium of Suffolk. L. Anatina, fig. 219, is so named from its
    resemblance to a duck's bill.

    LINGULINA. D'Orb. A genus of microscopic Foraminifera.

    LINTHURIS. Montf. Conch. Syst. 2. 154. A genus of microscopic
    Foraminifera.

    LIP. See LABIUM and LABRUM.

    LIPPISTES. Montf. A genus of microscopic Foraminifera.

    LITHODOMUS. Cuv. ([Greek: Lithos], _lithos_, stone; [Greek: Dôma],
    _doma_, house.) _Fam._ Mytilacea, Lam.--_Descr._ Transverse, elongated,
    cylindrical, equivalve, with the extremities rounded, and the posterior
    extremity rostrated; umbones not prominent, terminal; hinge straight,
    destitute of teeth; ligament linear, most conspicuous within; muscular
    impressions two.--_Obs._ The shells composing this genus differ from
    Modiola, not only in the cylindrical form, but also in the circumstance
    from which the generic name is derived, i. e. of their living in
    stones. Thus, while the form and structure of the shell bring it near
    the Mytili or Muscle shells, the habits of the animal cause it to
    approach the Lithophagi, or rock-eating molluscs of Lamarck. L.
    Dactylus (fig. 161,) is the Mytilus Lithophagus of ancient authors.

    LITHOLEPAS. Bl. ([Greek: Lithos], _lithos_, stone, [Greek: lepas],
    _lepas_, rock.) De Blainville's name for LITHOTRYA, Sow.

    LITHOPHAGIDÆ. Lam. ([Greek: Lithos], _lithos_, stone; [Greek: Phagô],
    _phago_, eat or gnaw.) A family of the Conchifera Dimyaria, Lam.
    consisting of terebrating bivalves, gaping anteriorly, having no
    accessary valves; and containing the genera Saxicava, Petricola,
    Venerupis, to which are added other genera enumerated in explanation of
    figures 91 to 97. Notwithstanding the numerous genera which have been
    created, I think that the most convenient arrangement will be to reduce
    them to two, thus--

        1. PETRICOLA, with distinct cardinal teeth, including, Clothe,
        Venerirupis and Coralliophaga. Fig. 91, 92, 97.

        2. SAXICAVA, without teeth, including Biapholius, Hiatella,
        Sphænia, Byssomya, and Thracia. Fig. 93 to 96.

    LITHOTRYA. G. B. Sowerby. ([Greek: Lithos], _lithos_, stone; [Greek:
    truo], _truo_, to bore through.) _Fam._ Pedunculated Cirripedes,
    Lam.--_Descr._ Eight unequal valves, forming a laterally compressed
    cone, the lower central valves being very minute; pedicle fleshy, scaly
    at the upper extremity; fixed at the base in a patelliform shelly
    support.--_Obs._ This genus derives its name from the power possessed
    by the animal of making dwelling holes in stones or pieces of rock. The
    remarkable shelly cups at the base of the pedicle is regarded as
    analogous to the shelly base of the Balanus, so that this genus would
    form an intermediate link between the Sessile and Pedunculated
    Cirripedes of Lamarck. Fig. 39, L. dorsalis. West India Islands.

    LITIOPA. Ranz. _Fam._ Turbinacea, Lam.--_Descr._ "Shell not very thick,
    horny, with a slight epidermis, rather transparent, conical, with
    whorls somewhat rounded; the last being larger than all the rest
    together; with the apex pointed, longitudinally grooved; aperture oval,
    larger anteriorly than posteriorly, with the lips disunited, the right
    lip simple, separated from the left by a rather indistinct notch, or a
    slight emargination in the contour. The left lip slightly reflected
    backwards, so as to form a kind of salient margin with the anterior
    extremity of the columella, which is united, rounded, arcuated and
    slightly truncated at the anterior."--_Obs._ The Molluscous animals,
    whose shells are thus described, are found in the Mediterranean, and
    are remarkable for the power of suspending themselves from the sea-weed
    on which they live, by a thread resembling a spider's web. The general
    appearance of the shell presents a medium between Phasianella and
    Littorina, but it is apparently destitute of an operculum.

    LITTORINA. Fer. (_Littus_, the sea-shore.) _Fam._ Turbinacea,
    Lam.--_Descr._ Turbinated, thick; spire acuminated, consisting of few
    whorls, about one third of the axis in length; aperture entire, large,
    rounded anteriorly; outer lip thickened within, acute; columella rather
    flattened; operculum horny, spiral, with rapidly increasing
    volutions.--_Obs._ The shells composing this genus are known from Turbo
    and Phasianella by the horny operculum; and from Trochus, which has
    also a horny operculum, by the small number of the whorls. The
    Littorinæ, among which may be enumerated the common Periwinkle, are, as
    the name implies, found on sea shores, feeding upon seaweed, in all
    parts of the world. Fig. 363, _L. Vulgaris_.

    LITUACEA. Bl. The second family of Polythalamacea. Bl. The shells are
    described as chambered, symmetrical, convolute in part of their extent,
    but constantly straight towards the termination. The genus Spirula,
    which is admitted into this family, does not properly belong to it, any
    more than to the Lituolæ of Lamarck, in which it is also placed. It
    does not agree with the descriptions of either. This family partly
    corresponds with the "Lituolées," Lam. and contains the genera Lituola,
    Ichthyosarcolites, Spirula, Hamites and Ammonoceras.

    LITUACEA. Lam. A family of the order Polythalamous Cephalopoda, Lam.
    containing the genus Spirula, fig. 471.

    LITUITUS. Montf. SPIROLINA, Lam. Microscopic.

    LITUOLA. Lam. A genus of microscopic Foraminifera.

    LITUOLÆ. Lam. The third family of Polythalamous Cephalopoda, Lam. the
    shells of which are described as partially spiral, the last whorl
    continuing in a straight line. The transverse septa which divide the
    chambers, are in general pierced by a siphon which breaks itself off
    before it reaches the succeeding septum. This family contains the
    genera of microscopic Foraminifera Lituola and Spirolina. The genus
    Spirula, also placed in this family, does not by any means agree with
    Lamarck's definitions "the last whorl continuing in a straight line."

    LITUUS. Humph. CYCLOSTOMA? Lam.

    LIVID. (From _lividus_.) Of a pale, dull, blue colour. The adjective is
    sometimes used as a specific name. _Ex._ Conus _lividus_, Sanguinolaria
    _livida_.

    LOBARIA. Schum. SANGUINOLARIA rosea, Lam. (fig. 98) and other similar
    species.

    LOBATE or LOBED. Divided into parts.

    LOBATULA. Fleming. A genus composed of two very minute species of
    chambered shells. Serpula lobata and S. concamerata, Mont. Test. Brit.
    515.

    LOMASTOMA. Rafinesque. An imperfectly defined genus, probably belonging
    to the Limnacea.

    LONGITUDINAL. Lengthwise. Longitudinal striæ, ribs, &c. are those which
    radiate from the apex and follow the spiral direction of the whorls, in
    spiral shells; and from the umbo to the ventral margin in bivalves. The
    term "decourantes" is employed by French conchologists. The bands in
    Achatina, fig. 286, are longitudinal or spiral.

    LORIPEDES. Poli. A genus composed of species of LUCINA, Auct. in which
    the lunules are not prominent.

    LOTORIUM. Montf. A genus composed of species of TRITON, Auct. in which
    the aperture is effuse. T. Lotorium, fig. 400.

    LOTTIA. Gray. PATELLOIDA, Quoy and Gaimard.

    LUCERNA. Humph. A generic name applied to some species of Helix
    included in De Ferussac's sub-genus Helicogena.

    LUCERNELLA. Sw. A genus of "Lucerninæ," Sw. thus described: "Teeth on
    both sides of the aperture; surface regularly and distinctly striated.
    Circumference convex."

    LUCIDULA. Sw. A sub-genus of Lucerna, Humph. thus described: "Aperture
    transverse, both lips much thickened and united; the outer with
    marginal obsolete teeth at the base; umbilicus closed. Barbadensis,
    _Lam._ No. 49. p. 78. Fêr. Moll. pl. 47, 2, 3, 4."

    LUCINA. Brug. _Fam._ Nymphacea, Lam. Conchacea, Bl.--_Descr._
    Equivalve, inequilateral, orbicular, lenticular, radiately striated;
    hinge with, generally, two minute cardinal teeth, which are sometimes
    nearly obsolete, and two lateral teeth, on each side of the umbo in one
    valve, one in the other; ligament external, partly hidden by the
    margins of the valves when closed. Muscular impressions two in each
    valve, the anterior one produced into an elongated, ligulate band, the
    posterior short and semi-rotund; impression of the mantle not
    sinuated.--_Obs._ The shells of this genus resemble Amphidesma in
    general form, but are distinguished by the external ligament, the
    elongated muscular impression, and the want of a sinus in the palleal
    impression. East and West Indies, and European shores. Fig. 104, L.
    Tigerina.

    LUNULATE. (_Luna_, the moon, dim.) Moon-shaped, having the form of a
    crescent. Applied most frequently to muscular impressions. Semilunar is
    sometimes used, perhaps with greater accuracy, to express the same
    shape.

    LUNULE. An impression on the anterior dorsal margin of some bivalve
    shells. The similar impression on the posterior dorsal margin is called
    the _escutcheon_.

    LUPONIA. Gray. A genus composed of species of CYPRÆA, Auct. which are
    described as having the anterior of the columellar lip crossed by
    several irregular ridges, without any distinct marginal ones,
    internally narrow, flat; the shell pear-shaped, smooth, or
    cross-ribbed. _Ex._ C. Algoensis, Luponia Algoensis, Gray, fig. 447.

    LUTRARIA. Auct. (_Lutum?_ mud.)--_Fam._ Mactracea, Lam.--_Descr._ Thin,
    equivalve, inequilateral, transverse, oblong or ovate, gaping at both
    extremities; hinge with one double and sometimes one single cardinal
    tooth in each valve, and a triangular, oblique pit with a prominent
    margin, containing the ligament; muscular impressions distant; palleal
    impression having a large sinus.--_Obs._ This genus differs from Mactra
    in the entire absence or indistinctness of lateral teeth. Fig. 77, L.
    Papyracea. (Ligula, Leach.) Fig. 78. L. Solenoides. Sandy and muddy
    shores.

    LUTRICOLA. Bl. LUTRARIA. Lam. Fig. 77, 78.

    LYCOPHRIS. Montf. A microscopic fossil described as resembling
    NUMMULITES, but having a granulated surface.

    LYMNADEA. Sw. A sub-genus of "Mysca," Turton, in the family of Nayades,
    Lam. thus described: "Posterior hinge margin elevated and winged; the
    valves connate; the surface smooth. L. alata. _Sw._ _Ex._ Conch. (fig.
    48.) fragilis. _Sw._ Zool. Ill. compressa, _Lea._ Am. Tr. iii. pl. 12.
    f. 22." Sw. p. 379.

    LYMNEA. See LIMNEA.

    LYMNEUS. Lam. See LIMNEANA.

    LYONSIA. Turt. Inequivalve species of ANATINA, Auct. which have no
    spoon-shaped cavity in the hinge, but an accessary piece. L. striata,
    fig. 491, 2.

    LYRODON. Goldf. TRIGONIA?

    MACLURITES. Lesuour. Journ. des Scienc. Nat. Philad. t. 1. p. 312. pl.
    13. fig. 2, 3.

    MACOMA. Leach. VENUS tenuis, Bl. and similar species, described as
    "Clothed with an epidermis; striated, compressed, oval; the summits not
    very prominent; two bifid teeth upon the right valve and a single
    undivided one upon the left."

    MACRODITUS. Montf. LENTICULINA, Bl. A genus of microscopic
    Foraminifera.

    MACROSPIRA. Guild. A genus composed of HELIX octona, Auct. Macrospira
    aperta, Guild.

    MACROSTOMATA. Lam. ([Greek: Makros], _macros_, long; [Greek: stoma],
    _stoma_, mouth.) A family belonging to the first section of the order
    Trachelipoda, the shells belonging to which are described as haliotoid
    or ear shaped, with a very large aperture, destitute of an operculum.
    This family contains the following genera, which maybe thus
    distinguished.

        1. VELUTINA. Globose, with velvety epidermis. Fig. 337.

        2. STOMATIA. Ear-shaped; pearly within; including STOMATELLA. Fig.
        335, 336.

        3. SIGARETUS. The same, not pearly; including _Cryptostoma_. Fig.
        334.

        4. CORIOCELLA. The same, thin, transparent.

        5. HALIOTIS. The same, not thin, nor transparent; with holes;
        including _Padollus_. Fig. 338, 339.

        6. SCISSURELLA. Heliciform, with a slit near the aperture. Fig.
        340.

        7. PLEUROTOMARIA. Trochiform, with a slit at the edge of the
        aperture. Fig. 341.

    MACTRA. Auct. (_Mactra_, a kneading trough.) _Fam._ Mactracea, Lam.
    Conchacea, Bl.--_Descr._ Usually thin, equivalve, sub-equilateral,
    sub-trigonal, slightly gaping at the extremities; hinge with one
    cardinal tooth, divided into two parts, diverging from the umbo, with
    sometimes a very small laminar tooth close to its side; a deep
    triangular pit near the centre, containing the cartilage; one long,
    lateral tooth on each side of the umbo in one valve, received between
    two in the other; muscular impressions two, lateral; palleal impression
    with a small sinus.--_Obs._ This genus contains many species of
    beautiful shells found in various parts of the world, some are common
    in Britain. Fossil species are not numerous, they occur in the tertiary
    strata. Fig. 79 to 82.

    MACTRACEA. Lam. A family of the order Conchifera Dimyaria, Lam. Sect.
    Tenuipedes. The cartilage placed in a trigonal pit with a small
    external ligament. The genera may be thus distinguished.

        1. LUTRARIA. No lateral teeth, shell gaping. The short species
        constitute the genus _Ligula_. Fig. 77, 78.

        2. MACTRA. Lateral teeth, shell closed. This genus has been divided
        into Mactra, Mulinia, Schizodesma and Spisula, by Mr. Gray. Fig. 79
        to 82.

        3. GNATHODON. Teeth serrated, thick, one angular. Fig. 83.

        4. CRASSATELLA. Shell thick, lateral teeth. Fig. 84.

        5. AMPHIDESMA. A distinct external ligament, internal ligament
        oblique. Fig. 85.

        6. ERYCINA. A short tooth on each side of the cartilaginous pit in
        each valve. Including Mesodesma. Fig. 86.

        7. UNGULINA. Ligament flat, divided. Fig. 88.

    MACULATED. (From _Macula_, a spot.) Spotted or patched. This term is
    applied by conchological writers, to those shells which are coloured in
    spots or small patches. In the same sense it is also used as a specific
    name. As for instance, Cytherea maculata, fig. 167, c. and Hippopus
    maculatus, fig. 156.

    MAGAS. Sow. ([Greek: Magas], _magas_, a board, a deck.) _Fam._
    Brachiopoda, Lam.--_Descr._ Equilateral, inequivalve; one valve convex,
    with a triangular area, divided by an angular sinus in the centre; the
    other valve flat, with a straight hinge line and two small projections;
    a partial longitudinal septum, with appendages attached to the hinge
    within. Differing from Terebratula in having a triangular disc, and not
    a circular perforation. Magas pumilus, fig. 299. Fossil in chalk.

    MAGILUS. Montf. _Fam._ Cricostomata, Bl. Serpulacea, Lam.--_Descr._
    Thick, tubular, irregular, contorted; rounded above, keeled beneath,
    free; apicial extremity convolute, heliciform, ovate or sub-globose;
    aperture elliptical.--_Obs._ This shell when in a young state presents
    the characteristics of a regularly formed spiral univalve, living in
    holes in madrepores. As the madrepore increases in bulk, the animal
    gives an eccentric course to the shell, in order to have its aperture
    even with the surface, and leaving the nucleus or young shell behind,
    fills it up with calcareous matter to reside in the open extremity of
    the tube. Fig. 9, 10. Red Sea and Mauritius.

    MALACOTA. Schum. OTION. Leach.

    MALACOZOA. Bl. ([Greek: Malakos], _malacos_, soft; [Greek: Zôon],
    _zoon_, animal.) The type or general appellative in De Blainville's
    system, including all molluscous animals, excepting those with
    multivalve shells.

    MALDANIA. Lam. The second family of the order Annelides Sedentaria. The
    only genus of shells described in this family is Dentalium, fig. 2, to
    which may be added Pharetrium, König. fig. 3. It is doubtful however
    whether the latter do not belong to an unknown genus of Pteropodous
    Mollusca.

    MALEA. Valenciennes. A genus composed of DOLIUM latilabrum, Kiener, and
    other similar species.

    MALENTOZOA. Bl. ([Greek: Malakos], _malacos_, soft; [Greek: en], _in_,
    [Greek: temnô], _temno_, cut; [Greek: Zôon], _zoon_, animal.) Or
    articulated mollusca. The sub-type in De Blainville's system,
    comprehending those with multivalve shells.

    MALLEACEA. Lam. A family belonging to the order of Conchifera
    Monomyaria. Containing the following genera of irregular pearly
    bivalves.

        1. AVICULA. Hinge linear, simple, including _Meleagrina_. Fig. 163,
        164.

        2. PERNA. Hinge with linear grooves, including _Pulvinites_. Fig.
        166, 170.

        3. GERVILLIA. Shaped like Modiola, with irregular grooves. Fig.
        162.

        4. CRENATULA. Hinge with a series of pits. Fig. 168.

        5. CATILLUS. Like Perna, but more regular and convex. Fig. 167.

        6. MALLEUS. A triangular disc on the hinge, and two auricles. Fig.
        165.

    MALLEUS. Auct. (_Malleus_, a hammer.) _Fam._ Malleacea, Lam.
    Margaritacea, Bl.--_Descr._ Equivalve, inequilateral, foliaceous,
    trilobate, undulated, irregular, attached by a byssus passing through a
    sinus in one valve; hinge rectilinear, lengthened by two auricles; with
    a small disc under the umbones, containing the ligament, and a groove
    containing the cartilage; muscular impressions one in each valve,
    large, uniform, and one or two others extremely minute.--_Obs._ Malleus
    Vulgaris, the type of this genus, is a most singular shell, commonly
    called the "Hammer Oyster," from the peculiarity of its shape. It
    belongs to the Linnæan genus Ostrea, from which it differs in being
    attached by a byssus. Fig. 165, M. Vulgaris. Tropical.

    MAMILLARIA. Sw. A sub-genus of NATICA, corresponding with Polinices of
    Montfort, having the spire small and the umbilicus filled. _Ex._ Natica
    Mamilla, Auct. fig. 327.

    MAMMILLATED. (_Mammula_, a little teat.) A term applied to the apex of
    a shell when it is rounded like a teat. _Ex._ Voluta Vespertilio, fig.
    433.

    MARGARITA. Leach. (_Margarita_, a pearl.) A genus of small shells
    resembling the genus Trochus, from which it differs in having an
    operculum consisting of few whorls. M. tæniata, fig. 362. Mr. G. B.
    Sowerby, sen. has enumerated 15 species in a list accompanying the
    figures published by the author of this manual in Nos. 132 to 134 of
    his Conchological Illustrations.

    MARGARITACEA. Bl. The third family of Lamellibranchiata, Bl. The shells
    belonging to it are described as irregular, inequivalve, inequilateral,
    black or horny without, pearly within; hinge auriculated, scarcely
    developed, and without teeth. The ligament is variable and there is a
    large sub-central muscular impression. This family contains the genera
    Vulsella, Malleus, Pinna, Crenatula, Inoceramus, Catillus, Pulvinites,
    Gervillia and Avicula.

    MARGARITACEOUS. (_Margarita_, a pearl.) Pearly.

    MARGARITANA. Schum. A sub-genus of Uniones, composed of species having
    "one cardinal tooth." ALASMODON, Say. MYA Margaritifera, Linn.

    MARGARITIFEROUS. (_Margarita_, pearl; _fero_, to bear.) Pearl-bearing.
    Applied to shells which form pearls; as Meleagrina Margaritifera, or
    Pearl-bearing Oyster.

    MARGINAL. Near the margin or edge.

    MARGINATED. (_Margo_, edge.) Having an edge or border thicker than the
    rest of the shell, from which circumstance the little genus Marginella
    derives its name.

    MARGINELLA. (A little rim or border.) _Fam._ Columellaria, Lam.
    Angyostomata, Bl.--_Descr._ Ovate, smooth, shining, with a short,
    sometimes hidden spire; aperture narrow, emarginated; columella with
    several oblique folds; outer lip neatly reflected.--_Obs._ This genus
    of pretty little shells differs from Voluta, in the reflection of the
    outer lip. The animal covers the greater part of the shell with the
    mantle, and by continually depositing vitreous matter gives it a bright
    polish, which, together with the delicately neat arrangement of colours
    in most species, renders them exceedingly beautiful. The Marginellæ are
    marine and tropical. A few fossil species are found in the
    Calc-grossier. Fig. 437. M. Glabella. GLABELLA, Sw.

    MARGINULINA. D'Orb. A genus of microscopic Foraminifera.

    MARINE CONCHACEA. See CONCHACEA.

    MARINE TESTACEA. Those shell-fish which inhabit seas, lakes, &c. of
    salt water, in distinction from the _Aquatic_ Testacea, or those which
    are found in rivers, ponds or stagnant pools of fresh water: and also
    from the _Land_ Testacea, which live on land and breathe air. The great
    proportion of shells belong to the former class, those of the latter
    two classes being limited in their number, and in the genera to which
    they belong.

    MARINULA. King. A genus of small shells resembling Auricula and
    Pedipes, described as "Ovate, sub-solid, with aperture ovate entire;
    columella bidentate, uniplicated towards the base, with large
    sub-remote teeth; the largest uppermost; no operculum."

    MARMAROSTOMA. Sw. A genus of "Trochidæ," Sw. thus described: "Umbilicus
    deep; spire of few whorls, much depressed, and obtuse; inner lip
    obsolete; base even more produced than in _Senectus_, but never
    distinctly channeled. M. versicolor. Mont. 176. f. 1740, 1741,
    undulata. Chem. 169. f. 1640, 1641," Sw. p. 348.

    MARPESSA. Gray. A sub-genus of Clausilia, C. bidens, &c. Auct. Gray's
    Turton, p. 212.

    MARTESIA. Leach. A genus composed of those species of PHOLAS, Auct.
    which are described as short, cuneiform, nearly closed at both
    extremities, having several accessary pieces on the middle of the back,
    and two marginal, lower down.

    MEASUREMENT. The most approved method of stating the measurements of
    various kinds of shells is as follows: _symmetrical convolute
    univalves_, the length is from anterior to posterior; the depth from
    ventral to dorsal; the breadth, from side to side of the aperture. Of
    _symmetrical conical univalves_, length, from front to back; breadth
    from side to side; depth from apex to base. Of _spiral univalves_,
    length, from apex to anterior of the columella or axis of the shell;
    breadth, across from the outer lip to the opposite side. Of
    _non-symmetrical bivalves_, the length is from the anterior to the
    posterior margin; breadth, from the greatest convexity of one valve to
    the corresponding part of the other; depth, from the ventral to the
    dorsal margin.

    MEGADESMA. Bowd. ([Greek: Megas], _megas_, great; [Greek: desma],
    _desma_, ligament.) POTAMOPHILA, Sow. GALATHÆA, Lam.

    MEGADOMUS. Sw. A sub-genus of Unio, thus described: "Only one lateral
    tooth in each valve; cardinal teeth two; posterior hinge margin winged.
    M. gigas, _Sw._" Sw. p. 378.

    MEGALODON. Sow. ([Greek: Megas], _megas_, great; [Greek: odos], _odos_,
    tooth.) _Fam._ Cardiacea, Lam.--_Descr._ Equivalve, longitudinal,
    acuminated at the umbones, thick; hinge forming an incrassated septum
    across the cavity of the shell, with a large bifid tooth in the right
    valve, and one irregular and one pointed in the left; ligament long,
    external.--_Obs._ The general form, the thickened hinge reaching across
    the cavity of the valve and the terminal umbones serve to distinguish
    this genus from Cardita, to which, however, it is nearly allied. M.
    cucullatus, fig. 127.

    MEGALOMASTOMA. Guild. A sub-genus of Cyclostoma, thus described:
    "Cylindrical, resembling _Pupa_, but has a horny operculum; spire not
    thickened; teeth or fold on the pillar none, flavula _Sw._ En. Méth.
    461. f. 6, brunnea _Guild._ (_fig. 97. g. h. 1._)" Sw. p. 336. Mr. Gray
    applies the name to those species which have "a groove or ridge in
    front of the mouth near the pillar."

    MEGARIMA. Rafinesque. A genus proposed to include species of
    TEREBRATULA, Auct. which are smooth and nearly equivalve. T. lævis, T.
    crassa, T. truncula.

    MEGASPIRA. Lea. ([Greek: Megas], _megas_, great, and spire.) M.
    Ruschenbergiana, (fig. 294) is a pupiform land shell remarkable for the
    length of its spire, which consists of no less than twenty-five close
    set, narrow, gradually increasing whorls. The outer lip is simple,
    slightly thickened; the inner lip has a tooth on the body-whorl, and
    two folds on the columella. Only one species of this singular shell is
    known.

    MEGATREMA. Leach. A genus composed of those species of Pyrgoma, Auct.
    which have a large aperture. Fig. 33.

    MELACANTHA. Sw. A sub-genus of Melania. Sw. p. 341.

    MELAFUSUS. Sw. A sub-genus of Melanopsis. Sw. p. 341.

    MELAMPUS. Montf. CONOVULUM, Lam. A genus composed of species of
    AURICULA, Auct. of a conical form. A. conoidalis, fig. 298.

    MELANIA. Auct. ([Greek: Melas], _melas_, black.) _Fam._ Melaniens, Lam.
    Ellipsostomata, Bl.--_Descr._ Turrited; spire generally elongated,
    acute; aperture entire, oval or oblong, pointed at the posterior
    extremity, rounded anteriorly, with a kind of indistinct canal or
    sinuosity: epidermis thick, generally black.--_Obs._ In common with
    other fresh-water shells, the Melaniæ are frequently found with
    corroded apices. This genus is known from Melanopsis by the absence of
    the notch at the anterior part of the aperture. The Melaniæ occur in
    rivers of warm climates. The fossil species are frequent in upper
    marine formations. Fig. 313, M. subulata.

    MELANIANA. Lam. (Melaniens.) A family belonging to the first section of
    the order Trachelipoda. The genera contained in it maybe distinguished
    as follows.

        1. MELANOPSIS. Aperture notched; columellar lip thickened above;
        including _Pirena_. Fig. 315, 316.

        2. MELANIA. Aperture not notched; columellar lip not thickened;
        including _Auculosa_, _Pasithæa_, _Io_. Fig. 313, 314, 317.

    MELANITHES. Sw. A sub-genus of Melanopsis. Sw. p. 341.

    MELANOIDES. Olivier. MELANOPSIS. Fer.

    MELANOPSIS. Fer. _Fam._ Melaniana, Lam. Entomostomata, Bl.--_Descr._
    Oval or oblong, fusiform; spire acute, sometimes elongated; aperture
    oblong or oval, pyriform, with a distinct notch at the anterior
    extremity; columella tortuous, callous, thickened at the extremity near
    the spire; epidermis thick, horny, generally black.
    Subtropical.--_Obs._ This description includes the two first species of
    the genus Pirena, Lam. The Melanopsides are known from the Melaniæ by
    the notch in the aperture. Fig. 315. M. costata.

    MELAS. Montf. MELANIA, Auct.

    MELATOMA. Sw. A sub-genus of Melanopsis. Sw. p. 341.

    MELEAGRINA. Lam. MARGARITA. A genus composed of the Pearl Oyster and
    similar species, separated from Avicula on account of the roundness of
    their general form, but re-united by Sowerby. For generic characters,
    see Avicula. Fig. 164. M. margaritifera.

    MELEAGRIS. Montf. TURBO Pica, Auct. and similar species, having the
    aperture oblique, the columella gliding imperceptibly into the outer
    lip, and having an umbilicus.

    MELINA. Schum. PERNA, Auct.

    MELO. Brod. (_Melo_, a melon.) _Fam._ Columellaria, Lam.--_Descr._
    Light, ventricose, oval, with a light greenish brown epidermis, spire
    short, papillary, regular, sometimes hidden by the last whorl; aperture
    large, nearly as long as the whole shell, emarginated anteriorly; outer
    lip thin; columella slightly curved, with four or five laminar,
    oblique, prominent plaits.--_Obs._ The genus Melo has been separated
    from _Voluta_ principally on account of the largeness of the aperture,
    the lightness of the shell and the thinness of the outer lip. Melo
    differs from Cymba in the regularity of the spiral apex, and in the
    greater rotundity of the shell. The Melons are beautifully coloured
    large shells, found in the seas of the old world. The Melo Indicus has
    a certain resemblance to a Melon. Fig. 435. M. Æthiopicus.

    MELONIA or MELONITES. A genus of microscopic Foraminifera.

    MERCENARIA. Schum. VENUS Mercenaria, Auct. The Money shell which passes
    current for cash, under the name "Wampum," among the North American
    Indians.

    MERETRIX. Lam. Original name for Cytherea, Lam.

    MEROE. Schum. CYTHEREA Meroe, sulcata, scripta, hians, Auct. and
    similar species. Fig. 117, a.

    MESODESMA. Desh. ERYCINA, Lam. according to G. B. Sowerby.

    MESOMPHYX. Rafinesque. A genus proposed to be separated from HELIX,
    Auct.

    MICROTOMA. Sw. A genus of "Purpurinæ," Sw. thus described, "Pillar very
    broad and curving inwards; aperture effuse; the notch at the base small
    and nearly obsolete; spire very short, patula. Mart. 69. f. 758, 759.
    persica. En. Méth. 397. f. 1. unicolor. _Sw._ Chem. f. 1449. Sw. p.
    301." Purpura Persica. Fig. 414.

    MILIOLA. Lam. A genus of microscopic Foraminifera.

    MISILUS. Montf. A genus of microscopic Foraminifera.

    MITRA. Lam. (_Mitre._) _Fam._ Columellaria, Lam. Angyostomata;
    Bl.--_Descr._ Oblong, thick, covered with a light brown epidermis;
    spire long, turrited, acute; aperture emarginated anteriorly; outer lip
    thickened; columella with several oblique, thick plaits.--_Obs._ The
    pretty small shells composing this genus differ from Marginella, not
    only in general form, but in the outer lip not being reflected. Some
    species of Voluta, of a more elongated shape than the rest, present a
    near approach to the most ventricose of the Mitræ. The apex of Mitra,
    however, is always acute, while that of Voluta is generally papillary.
    The aperture of the former is narrow and the inner lip thickened, the
    contrary being the case with the latter. The shells of this genus are
    varied in colouring which is generally rich; and also in form, some
    being angulated, some plicated, some coronated and others smooth. The
    species are mostly tropical; very few occur so far north as the
    Mediterranean. Fossil species are numerous in the Eocene beds. Fig.
    431. M. Plicaria. Fig. 432. Conohelix marmorata, Sw.

    MITRELLA. Sw. A genus consisting of MITRA Fissurella, casta,
    Olivæformis, and similar species, described as "Rather small;
    olive-shaped; unequally fusiform; always smooth and polished, and
    sometimes covered with an epidermis; base obtuse and effuse; spire
    nearly or quite equal to the aperture; plaits of the pillar few,
    oblique, and extending beyond the aperture, which is smooth
    internally." Sw. p. 321. M. Fissurata, E. M. 371. f. 1. Olivarii, f. 2.
    Dactylus. 372. f. 5. _Ex._ Mitra bicolor.

    MITREOLA. Sw. A genus of "Mitranæ," Sw. thus described: "Small;
    unequally fusiform; the base obtuse; inner lip, typically thickened,
    inflected, and either toothed or tuberculated; plaits on the pillar
    distinct, the inferior largest; tip of the spire sometimes papillary;
    aperture without either striæ or groove." Sw. p. 320, M. Monodonta, M.
    Terebellum. Zool. Illustr. II. 128. f. 1. f. 2.

    MODIOLA. Lam. (_Modiola_, a little measure.) _Fam._ Mytilacea,
    Lam.--_Descr._ Equivalve oblique, cuneiform, inequilateral, thin, with
    the anterior side short and narrow, slightly gaping to admit the
    passage of a byssus, and the posterior side elongated, broad,
    sub-quadrate; hinge thin, toothless, rectilinear, with a long, partly
    external ligament; muscular impressions two in each valve; palleal
    impression irregular, not sinuated.--_Obs._ This genus differs from
    Mytilus, to which the common muscle belongs, in the anterior margin
    being rounded out beyond the umbo, which in Mytilus is terminal. The
    Lithodomi may be known from this genus by their cylindrical form. Fig.
    160, M. Tulipa.

    MOLLUSCA. (From _Mollis_, soft.) The twelfth class of invertebrated
    animals with univalve shells or none; divided into the following
    orders: Pteropoda, Gasteropoda, Trachelipoda, Cephalopoda, Heteropoda,
    fig. 220 to 488. The term mollusca is also used in a general sense to
    include the classes Conchifera and Mollusca of Lamarck, corresponding
    with the type Malacozoa of De Blainville.

    MONEY COWRY. Cypræa Moneta, which passes current in some parts of
    Africa and the East Indies.

    MONILEA. Sw. A sub-genus of Monodonta. Sw. p. 352.

    MONOCEROS. ([Greek: Monos], _monos_, single; [Greek: Keras], _ceras_,
    horn.) _Fam._ Purpurifera, Lam.--_Descr._ Ovate, thick, covered with a
    brown epidermis; spire short, consisting of few whorls; aperture
    emarginated anteriorly; columella rather flat; outer lip thick, with a
    prominent tooth near the extremity.--_Obs._ This genus resembles
    Purpura, in every respect, except in having the tooth from which the
    name is derived. A catalogue of 16 species by Mr. Sowerby, sen. is
    published with figures of 14, in parts 58 to 67 of the Conchological
    Illustrations by the author. The species belong to the South American
    coasts of the Pacific Ocean.

    MONOCONDYLÆA. D'Orb. A sub-genus of Uniones, described as equivalve,
    inequilateral, sub-rotund or angulated; hinge consisting of a large,
    obtuse, round cardinal tooth in each valve, with no lateral teeth.
    Monocondylæ (Unio) Paraguayana, D'Orb. fig. 149.

    MONODONTA. Lam. ODONTIS, Sow. A genus separated from Trochus, Auct. on
    account of the tooth or notch with which the columella abruptly
    terminates. M. labeo, fig. 366.

    MONOICA. Bl. The second sub-class of the class Paracephalophora, Bl.
    divided into the orders Pulmobranchiata, Chismobranchiata,
    Monopleurobranchiata, in the first section; and Aporobranchiata,
    Polybranchiata, Cyclobranchiata, Inferobranchiata, and
    Nucleobranchiata, in the second.

    MONOMYARIA. Lam. ([Greek: Monos], _monos_, single; [Greek: muon],
    _myon_, muscle.) The second order of Conchifera, consisting of those
    bivalve shells which have but _one_ principal muscular impression in
    each valve. The Monomyaria are thus divided: First section, containing
    the families Tridacnacea, Mytilacea, Malleacea; second section,
    containing the families Pectinides, Ostracea; third section, containing
    the families Rudistes, Brachiopoda.

    MONOPLEUROBRANCHIATA. Bl. The second order of the first section of
    Paracephalophora Monoica. Bl. The animals are described as having the
    lungs branched, situated at the right side of the body and covered more
    or less completely by the operculiform mantle, in which there is
    sometimes enveloped either a flat or a more or less involute shell,
    with a large entire aperture. They have either rudimentary or auricular
    tentacula, or none. This order, which includes mollusca with haliotoid
    or patelliform shells, is divided into the following families: _Fam._
    1. Subaplysiacea; 2. Aplysiacea; 3. Patelloidea; 4. Acera.

    MONOPTYGMA. Lea. A genus of small shells resembling Tornatella, but
    having a strong, oblique fold in the centre of the columellar lip. M.
    Elegans, fig. 344.

    MONOTHALAMIA. ([Greek: Monos], _monos_, single; [Greek: thalamos],
    _thalamos_, chamber.) The second division of Cephalopoda, Lam.
    containing only one genus, namely Argonauta.

    MONOTHYRA. A term used by Aristotle to designate spiral univalves.

    MONOTIGMA. Gray. A genus founded on the species represented fig. 371.
    It is a turrited shell, but we are unacquainted with the characters of
    the genus.

    MORIO. Montf. CASSIDARIA, Auct. C. Echinophora, fig. 407.

    MOTHER OF PEARL. This beautiful substance, which is so much resorted to
    for ornamental purposes, constitutes the thickened coating of the
    internal surface of the shell named by scientific collectors,
    Meleagrina Margaritifera, commonly called the Pearl Oyster, a young
    specimen of which is figured (164) in our plates. The reason why this
    substance is called mother-of-pearl is that the true pearls are
    produced from its surface. They arise principally from accident or
    disease, and are sometimes artificially produced by pricking through
    the outside of the shell while the animal is living. The animal is
    allowed to live until it has formed a pearl over the wounded part.

    MOULINSIA. Grateloup. PUPINA, Vignard. A genus of small land shells
    with enamelled surface and spiral operculum. See PUPINA.

    MOURETIA. Gray. "_Gadin_," Adanson. A genus of patelliform shells,
    described as differing from SIPHONARIA (the original Mouretia of
    Adanson) in the situation of the siphon, which in Mouretia is close to
    the place where the muscular impression is interrupted to leave a space
    for the head; while in Siphonaria it is nearly half way between the
    anterior and posterior ends of the shell.

    MOUTH. The aperture or opening of univalve shells.

    MULINIA. Gray. A genus composed of species of MACTRA, Auct. described
    as having the ligament (properly so called) internal, and lateral teeth
    simple. _Ex._ fig. 82. M. bicolor; Mactra, Auct.

    MULLERIA. Fer. _Fam._ Ostracea, Lam.--_Descr._ Irregular, subquadrate,
    inequivalve, inequilateral, foliaceous, attached, pearly within, green,
    horny without; hinge irregular, with a partly external ligament,
    passing to the interior, through a sort of sinus.--_Obs._ This
    remarkable shell resembles Etheria in general form and appearance, but
    is distinguished by having only one muscular impression. It is so rare
    that, although not very beautiful, a specimen has been known to produce
    £20. at a sale. Fig. 192.

    MULTILOCULAR. Many chambered.

    MULTISPIRAL. (_Multus_, many, _spira_, spire.) A term applied to a
    shell when the spire consists of numerous whorls; or to an operculum of
    numerous volutions.

    MULTIVALVE. (_Multus_, many; _valva_, valve.) Consisting of numerous
    valves. There are three kinds of multivalve shells: 1st. Those in which
    the valves are arranged in pairs, and produce a flattened figure, as
    Pedunculated Cirripedes, fig. 34 to 43; 2nd. Those in which they are
    arranged circularly, as Sessile Cirripedes, the valves of which are of
    two kinds; the _opercular_, consisting of several valves, which close
    the aperture, and the _parietal_, consisting of those which surround
    the body of the animal in a circular form, fig. 14 to 33. 3rd. Those in
    which they are arranged in a straight line, as Chiton, fig. 227.

    MUREX. Auct. (_A sharp rock._) _Fam._ Canalifera, Lam. siphonostoma,
    Bl.--_Descr._ Turrited, ventricose, thick, with three or more
    longitudinal, continuous, branched, spinose or fringed varices; spire
    prominent, acute; aperture oval, terminating in a posterior, partly
    closed canal, outer lip varicose, inner lip smooth, laminar; operculum
    horny, concentric, pointed.--_Obs._ This genus contains some of the
    most exquisitely beautiful shells in existence, the richness of their
    colouring, the ramifications of their varices, would render most
    species the finest possible subject for the exercise of the painter's
    art in still life. The most remarkable are the Rosebud Murex, with its
    pink-tipt fringes, the Venus Comb, with its long rows of parallel
    spines; the Ducal Murex, the Royal Murex, and many others, which are
    much sought after by collectors. Murex may be distinguished from Triton
    by the continuity of the varices, which follow each other in a tortuous
    direction on the spire. The Ranellæ have only two rows of varices, and
    have a posterior as well as anterior canal; while Murices have three or
    more varices, and only one canal. The genus Typhis consists of several
    small species resembling Murex in every respect, excepting that of
    having a tubular opening on the upper part of the whorl between each
    varix. See TYPHIS. The most beautiful Murices are brought from tropical
    climates. Fig. 395, 396.

    MURICANTHUS. Sw. A sub-genus of Murex, thus described: "Varices
    numerous, foliated; spire short; margin of the outer lip with a
    prominent tooth near the base; Radix. _Sw._ Zool. Ill. 2nd series. pl.
    113, Melanomathus. En. Méth. 418. f. 2." Sw. p. 296. The latter of the
    two species quoted, however, does not agree with the description,
    having no prominent tooth on the margin of the outer lip.

    MURICATED. (_Muricatus._) Having sharp points or prickles.

    MURICIDEA. Sw. A genus of "Muricinæ," Sw. thus described, "Spire more
    produced, as long or longer than the body whorl; varices numerous; no
    internal channel at the top of the aperture." Sw. p. 297, and
    consisting of the following incongruous species, "Lamellosa. Chem. f.
    1823, 4. magellanica. En. M. 419. f. 4. peruviana. Ib. f. 5. senticosa,
    Ib. f. 3. scaber. En. Méth. 419. f. 6. hexagona. Ib. 418. f. 3.
    erinacea. Mart. f. 1026." Sw. p. 297.

    MUSCULAR IMPRESSIONS are the marks or areas formed on the interior
    surface of shells by the muscular fibres which attach the animals to
    them. Lamarck has divided his Conchifera into two kinds: 1st.
    Monomyaria, those which have but one adductor muscle, and consequently
    have but one impression in each valve, as the common Oyster, fig. 180;
    2nd. The Dimyaria, those which have two, and consequently have two
    impressions in each valve. There are other smaller impressions in some
    shells besides the principal. The palleal impression is a mark or scar
    passing near the margin of the shell. See Introduction.

    MYA. Auct. _Fam._ Myaria, Lam. Pyloridea, Bl.--_Descr._ Transverse,
    oval, thick, gaping at both extremities, rounded anteriorly, acuminated
    posteriorly; hinge with one large, dilate, compressed tooth in one
    valve, and a suture in the other, containing the cartilage; muscular
    impressions two, distant, large, irregular; palleal impression with a
    large sinus.--_Obs._ Mya may be known by the large, prominent, broad
    tooth in one valve. In Anatina there is one in each valve, and, in
    Lyonsia, accessory pieces. Lutraria has cardinal teeth and a
    ligamentary pit. Few species of Mya are known. They belong to the
    Northern Hemisphere. M. truncata, fig. 71.

    MYCETOPODA or MYCETOPUS. D'Orb. _Fam._ Nayades, Lam.--_Descr._ Shell
    elongated, soleniform, inequivalve, inequilateral, gaping anteriorly;
    muscular impressions very complex.--_Obs._ These shells are said to
    terebrate like Pholas. Fig. 151. M. solenoides.

    MYARIA. Lam. A family belonging to Lamarck's order Conchifera Dimyaria.
    Containing the following genera:

        1. ANATINA. Ligament in a spoon-shaped prominence on the hinge of
        each valve, shell thin. Fig. 69.

        2. MYA. Spoon-shaped prominence in one valve; shell thick. Fig. 71.

        3. ANATINELLA. A spoon-shaped process in both valves. Fig. 70.

        4. LYONSIA. An internal bony appendage on the hinge. Fig. 491, 492.

        5. MYOCHAMA. Flat valve attached, a bony appendage on the hinge.
        Fig. 73.

        6. CLEIDOTHÆRUS. Deep valve attached, a bony appendage. Fig. 75,
        76.

        7. CUMINGIA. Ligamentary pit in both valves, spoon-shaped. Fig. 87.

    MYOCHAMA. Stutch. (_Mya_ and _Chama_.) _Fam._ Myaria, Lam.--_Descr._
    Inequivalve, irregular, attached, subequilateral; attached valve flat,
    with two marginal, diverging teeth, and one end of a little testaceous
    appendage fixed between them by a horny cartilage; free valve convex,
    with umbo incurved and two very minute, diverging teeth, between which
    the other end of the testaceous appendage is placed; external surface
    of both valves conforming to the grooves or undulations of the shell to
    which the specimen is attached; muscular impressions two in each valve;
    palleal impressions with a short sinus.--_Obs._ This new genus, of
    which only one species is known, the M. anomioides from New South
    Wales, differs from Anomia and Anatina in being attached by the surface
    of one of the valves, from which circumstance the word Chama is added
    to its name; the little testaceous appendage bringing it near the
    Myariæ. Fig. 73, M. anomioides.

    MYOCONCHA. Sow. (_Mya_ and _Concha_.) _Fam._ Cardiacea, Lam.--_Descr._
    Oval, equivalve, oblique; umbones terminal; ventral margin rounded;
    hinge with an external ligament, and one oblique, elongated tooth in
    the left valve; impression of the mantle not sinuated.--_Obs._ The
    fossil genus has the general form of Mytilus or Modiola, but the hinge
    of the Conchæ generally.

    MYOPARA. Lea. (_Myoparo_, a piratical oar-galley.) _Fam._ Arcacea, Lam.
    A genus founded on a minute fossil bivalve shell, somewhat resembling
    Isocardia in form, but having a series of teeth placed on each side of
    the umbones. M. costatus, fig. 135.

    MYRISTICA. Sw. A genus of "Pyrulinæ," Sw. thus described:
    "Sub-pyriform; spire strong, spiny, or tuberculated, nearly as long as
    the base; umbilicus either partially or entirely concealed; inner lip
    vitreous, thin; the outer with an internal and ascending canal; the
    basal channel wide. Hippocastanea. En. M. 432. f. 4. lineata, Ib. f. 5.
    melongena. En. Méth. 435. f. 3. nodosa. Chem. 1564. 5." Sw. p. 307.
    _Ex._ P. Melongena, Fig.

    MYRTEA. Turt. VENUS spinifera, Auct. LUCINA spinifera, Nonnull. The
    shells of this genus are described as "Oval, triangular, equivalve,
    nearly equilateral, closed. Hinge of one valve with a single tooth, and
    lateral one on each side; of the other valve with two teeth, the
    lateral ones obscure. Ligament external." British Channel and
    Mediterranean.

    MYSCA. Turt. A genus composed of species of UNIO, Auct. which are
    distinguished by having "strong, transverse, notched, cardinal and long
    lateral teeth." Unio pictorum.

    MYSIA. Leach. A genus composed of TELLINA rotundata, montagu and other
    similar species.

    MYTILACEA. Bl. The fourth family of Lamellibranchiata, Bl. The shells
    are described as regular, equivalve, frequently with a thick, horny
    epidermis. A toothless hinge and a linear ligament. This family
    contains the genera Mytilus and Pinna.

    MYTILACEA. Lam. A family belonging to the first section of Conchifera
    Monomyaria, Lam. described as having the ligament partly interior,
    occupying the greater part of the hinge line, which is straight. The
    shell is rarely foliaceous. The Mytilaceæ cannot easily be confounded
    with the Malleaceæ, because the former are generally regular and the
    latter are irregular, and have a thick internal coating of pearl,
    beyond which the external coating extends. The genera may be thus
    distinguished:

        1. MYTILUS. Umbones terminating in a point. Fig. 158.

        2. DREISSINA. The same, with a septiform plate. Fig. 159.

        3. MODIOLA. Anterior margin rounded beyond the umbones. Fig. 160.

        4. PINNA. Open at the posterior extremity. Fig. 162.

        5. LITHODOMUS. Cylindrical, living in holes. Fig. 161.

    MYTILUS. Auct. _Fam._ Mytilacea. Lam.--_Descr._ Equivalve, cuneiform,
    oblique, smooth, with umbones terminal, pointed, and posterior side
    broad, rounded; hinge linear, with a long, partly internal ligament;
    muscular impressions two in each valve, that on the posterior side
    large, irregular; that on the anterior small; palleal impression
    irregular.--_Obs._ The Linnean genus Mytilus included the Modiolæ,
    which differ from the Mytili in the rounded anterior side; and the
    Pinnæ, which are large shells, gaping at the posterior extremity. M.
    achatinus, fig. 158.

    NÆARA. Gray. A genus composed of ANATINA longirostrum, Lam. and other
    similar species.

    NAIA. Sw. A sub-genus of Castalia, Lam. thus described: "Oval, cardinal
    teeth beneath the bosses, and deeply sulcated, C. corrugata. _Lam._ En.
    Méth. 248. f. 8, picta. _Sw._ En. Méth. 248. f. 6." Sw. p. 379.

    NANINIA. Gray. A genus composed of the planorbicular species of HELIX,
    with large umbilici, and outer lip thin, included in the sub-genus
    Helicella, Fer. _Ex._ H. citrina, fig. 280.

    NASSA. Lam. A genus of small shells united to Buccinum by some authors,
    but separated by others on account of the little tooth-like projection
    terminating the columella. N. arcularia, fig. 423.

    NATICA. Brug. _Fam._ Neritacea, Lam. Hemicyclostomata, Bl.--_Descr._
    Globose, thick, generally smooth; spire short, pointed, with few
    volutions; aperture semilunar, entire; outer lip thin; columellar lip
    oblique, nearly straight, callous; umbilicus with a spiral callosity,
    terminating behind the columella, and sometimes filling up the cavity;
    operculum shelly in some species, horny in others; epidermis thin,
    light, semitransparent.--_Obs._ The straight, callous, smooth edge of
    the columella and the callosity serve to distinguish this genus from
    Nerita, Neritina, Neritopsis and Helix. Fig. 327, 328.

    NATICARIA. Sw. A sub-genus of Natica, thus described: "Oval; convex
    above; umbilicus small, open, placed very near the top of the aperture;
    inner lip reflected; small. N. melanostoma, Mart. 189. f. 1926, 1927.
    cancellata, _Sw._ Ib. 189. f. 1939. bifasciata, Griff. Cuv. 1. f. 2."
    Sw. p. 346.

    NATICELLA. Guild. A sub-genus of Natica, thus described: "Operculum
    horny; shell globose, but generally depressed; umbilicus nearly filled
    up by a vitreous deposition of the inner lip; spire obtuse. N.
    aurantia. Mart. 189. f. 1934, 1935." Sw. p. 345.

    NAVICELLA. Lam. (_A little ship._) _Fam._ Neritacea, Lam.
    Hemicyclostomata, Bl.--_Descr._ Transversely oval, symmetrical, smooth;
    aperture entire, oval; dorsal surface convex; outer lip thin; inner lip
    flat, straight edged; spread over the front surface of the body whorl,
    and sometimes hiding the apex; apex incurved; operculum testaceous,
    flat, sub-quadrate, with a lateral articulation.--_Obs_. This well
    known genus, of which there are several species, is named Cimber by
    Montfort. The shells are brought from India, the Isle of France and the
    Moluccas. Fig. 323, N. elliptica.

    NAUTELLIPSITES. Parkinson. A generic name proposed to include such
    species of Nautilus as have been compressed, so as to assume an oval
    instead of a round form. The genus Ellipsolites of De Montfort consists
    of species of Ammonites similarly deformed.

    NAUTILACEA. Bl. The fifth family of Polythalamacea, Bl. the shells of
    which are described as more or less discoidal, compressed,
    symmetrically convolute; the last whorl much longer than the others;
    which are entirely hidden beneath it and advancing beyond the last but
    one, so as constantly to form a large oval aperture, which is always,
    however, modified by the last whorl. The septa are united in the
    greater number of instances and pierced by one or more (?) siphons.
    This family contains the genera Orbulites, Nautilus, Polystomella and
    Lenticulina.

    NAUTILACEA. Lam. The sixth family of Polythalamous Cephalopoda, Lam.
    containing the genera Discorbites, Siderolites, Polystomella,
    Vorticialis, Nummulites, Nautilus. To these may be added Simplegas and
    Endosiphonites. Fig. 472 to 476.

    NAUTILUS. Auct. (_A little boat._) _Fam._ Nautilacea, Lam. and
    Bl.--_Descr._ Convolute, discoid, chambered, symmetrical; spire partly
    or entirely concealed by the last whorl; aperture modified by the last
    whorl, wide, sinuated on the dorsal margin; interior surface pearly;
    septa dividing the chambers simple; siphon discontinuous.--_Obs._ The
    shell named Nautilus by Pliny is the Argonauta of modern authors, a
    thin shell, not chambered. The Nautili are known from the Ammonites by
    the septa being simple, not sinuated as in the latter genus, and in
    general the volutions of the spire are not visible. Three or four
    species are known inhabitants of the Pacific Ocean and Australian
    Ocean. The fossil species are found in the tertiary, and also in the
    secondary strata, as low down as the Mountain limestone. N. pompilius,
    Frontispiece.

    NAYADES. Lam. A family of the order Conchifera Dimyaria, Lam. described
    as containing fresh-water bivalve shells, with or without teeth on the
    hinge. They are all pearly within, and have a thick, rather smooth
    epidermis without. This family contains a great variety of shells,
    which have been separated into an immense number of genera, but which
    G. B. Sowerby, sen. gives very good reasons for uniting under one
    generic name. The most generally received distinctions are as follows:

        1. CASTALIA. Two cardinal, one lateral, ribbed teeth. This genus is
        removed from the family of Trigonacea. Fig. 140.

        2. UNIO. Teeth various. Fig. 142, 145, 149, 148, 147, 151, 141.

        3. HYRIA. Trigonal, alated. Fig. 143, 150.

        4. ANODON. No teeth. Fig. 152.

        5. IRIDINA. Hinge crenated. Fig. 150.

    NECTOPODA. Bl. The first family Nucleobranchiata, Bl. containing the
    genera Carinaria and Firola; the latter is not a shell.

    NEMATOPODA. Bl. The first class of the sub-type Malentozoa, Bl.
    containing all the mollusca with multivalve shells, except Chiton, and
    divided into the families Lepadicea and Balanidea, corresponding with
    Lamarck's sessile and pedunculated Cirripedes, and with the Linnæan
    genus Lepas.

    NEMATURA. Benson. _Fam._ Turbinacea, Lam.--_Descr._ Thin, nearly oval,
    somewhat compressed from back to front; spire acute, consisting of few
    rounded whorls; last whorl large, but contracted near the aperture;
    aperture small, oblique, rounded anteriorly; peritreme continuous,
    thin; operculum spiral, horny, with few volutions.--_Obs._ The
    distinguishing character of this genus is the contraction of the last
    whorl near the aperture, in which respect it is nearly resembled by the
    shell called Cyclostoma lucidum. Two recent and one fossil species, all
    very minute, are described by Sowerby in Loudon's Magazine of Natural
    History, New Series. Fig. 305.

    NERINEA. Defr. _Fam._ Canalifera, Lam.--_Descr._ Turrited, oblong,
    sub-canaliculated, consisting of numerous whorls; aperture with a
    strong fold on the columella, one on the outer lip, and one on the
    inner lip at the edge of the body whorl.--_Obs._ This genus is only
    found in a fossil state usually in the Oolitic beds, it is not
    resembled by any other; the strong, prominent folds on the three upper
    angles of the subquadrate aperture present a singular appearance in a
    section. One species has been named N. Hieroglyphus. We give N.
    Goodhallii, fig. 374.

    NERITA. Auct. _Fam._ Neritacea, Lam. Hemicyclostomata, Bl.--_Descr._
    Smooth or ribbed, semiglobose; spire short, sometimes flat, consisting
    of few volutions; aperture large, semilunar; outer lip thick, entire;
    inner lip thickened, dentated at the edge, spread over the body whorl,
    forming a flattened disc; operculum shelly, spiral, with an appendage
    by which it is locked under the sharp edge of the columella.--_Obs._
    These marine shells are known from Neritina by the thickness of the
    shell and the want of the thick, horny, dark coloured epidermis; from
    Natica by the flat area produced by the spreading of the thickened
    columellar lip. N. Peloronta, fig. 330. N. polita, fig. 329.

    NERITACEA. Lam. A family of the first order of Trachelipoda, Lam.
    containing the following genera:

        1. NAVICELLA. Apex terminal, not spiral; inner lip septiform. Fig.
        323.

        2. NERITA. Columellar lip septiform, edge with distinct teeth;
        shell thick. Fig. 330.

        3. NERITINA. Shell thin; columellar lip septiform, edge
        denticulated; generally a thick, dark coloured epidermis. Fig. 324
        to 326.

        4. NATICA. Having an umbilicus behind the columellar lip, with a
        spiral callosity. Fig. 327, 328.

        5. NERITOPSIS. Edge of the columellar lip with a deep notch. Fig.
        331.

        6. PILEOLUS. Patelliform; apex central; columellar lip septiform,
        leaving the aperture small. Fig. 332.

        7. JANTHINA. Columellar lip linear; aperture angulated. Fig. 333.

    NERITINA. Lam. _Fam._ Neritacea, Lam.--_Descr._ Thin, semiglobose,
    obliquely oval, smooth, flattish in front; spire short, sometimes
    depressed, consisting of few rapidly increasing whorls; aperture
    semicircular; outer lip thin, sharp; columellar lip broad, flat, its
    inner edge straight, denticulated; operculum testaceous, semicircular,
    sub-spiral, with an articulating process on the inner edge.--_Obs._
    This genus of fresh-water shells differs from Nerita in the minuteness
    of the denticulation of the columella, as well as in the characters
    mentioned in our observations upon the latter genus. N. spinosa,
    (Clithon, Montf.) fig. 325. N. virginea, fig. 324. N. perversa, Lam.
    (Velates, Montf.) fig. 326. All the species known up to the present
    time, with the exception of three, are represented in the author's
    Conchological Illustrations, parts 86, 87, 90, 91, 94 to 100. The
    catalogue accompanying these representations enumerates 59 species.

    NERITOPSIS. Gray. _Fam._ Neritacea, Lam.--_Descr._ Sub-globose, thick,
    cancellated; spire short, composed of few rapidly increasing whorls;
    aperture transverse, sub-orbicular; outer lip thickened within;
    columellar lip thick, rather flat, with a large rounded notch in the
    centre of its inner edge.--_Obs._ This genus most nearly resembles
    Nerita, from which it differs in the peculiar notch of the columella.
    N. granosa, fig. 331.

    NICANIA. Leach. ASTARTE, Sowerby. The same as CRASSINA of Lamarck.

    NITIDELLA. Sw. A genus of "Columbellinæ," Sw. thus described:
    "Bucciniform, small, ovate, smooth, glassy; aperture effuse; outer lip
    slightly thickened, faintly inflexed, and generally striated
    internally; inner lip somewhat flattened above; base of the pillar with
    one or two slight internal folds, or a single angular projection.
    Columbella nitida, _Lam._ (fig. 17, _c._ p. 151.)" Sw. p. 313.

    NOBIA. Leach. _Order_, Sessile Cirripedes, Lam. This genus resembles
    Pyrgoma, Auct. consisting of a conical paries, supported upon a
    funnel-shaped cavity in the madrepore, but differs in its operculum,
    which consists of two valves, whereas that of Pyrgoma has four. N.
    grandis, fig. 29.

    NODOSARIA. Lam. and ORTHOCERA have been united by Sowerby under the
    name of the first. _Fam._ Orthocerata, Lam. and Bl.--_Descr._ Straight,
    chambered, elongated; chambers more or less ventricose; septa
    perforated by a central siphon.--_Obs._ This genus consists only of
    fossils found in sub-appenine tertiary beds. It is placed by De
    Blainville in one of his divisions of the genus Orthoceras, which is
    characterized as "species not striated, and with chambers very much
    inflated." N. æqualis, fig. 465.

    NODOSE. Having tubercles or knobs.

    NOGROBS. Montf. A fossil appearing from the figure and description to
    resemble Belemnites.

    NONION. Montf. A genus of microscopic Foraminifera.

    NONIONINA. D'Orb. A genus of microscopic Foraminifera.

    NOTREMA. Rafinesque. A shell described as composed of three integral
    valves, concerning which De Blainville puts the query, "ne seroit-ce
    pas plutôt une Balanide mal observée?"

    NOVACULINA. Benson. (_Novacula_, a razor.) _Fam._ Solenacea,
    Lam.--_Descr._ Equivalve, inequilateral, transversely elongated;
    external ligament communicating with the interior of the shell by an
    oblique channel; beaks prominent; hinge line nearly straight, with one
    narrow curved cardinal tooth in one valve, entering between two similar
    teeth in the other; siphonal scar long; extremities of the shell
    gaping; epidermis thin, light brown, folding over the edges and
    connecting the dorsal margins. _Hab._ Jumna, Gooti, and Ganges. Fig.
    63.

    NUCLEOBRANCHIATA. Bl. The fifth order of the second section of
    Paracephalophora Monoica, Bl. the shells of which are described as
    symmetrical, more or less curved, or longitudinally rolled up and very
    thin. This order contains, _Fam._ 1. Nectopoda, containing Carinaria;
    _Fam._ 2. Pteropoda, containing Atlanta, Spiratella and Argonauta.

    NUCLEUS. (_A kernel._) Anything forming a centre around which matter is
    gathered. The nucleus of shells is the first formed part; the first
    deposit of shelly matter to which the successive layers are added; the
    apex of the spiral cone, of which most shells are composed. (See CONE.)
    The nucleus is formed within the egg in oviparous, and within the old
    shell in viviparous mollusca. It is frequently more transparent and
    light than the remainder of the shell, and sometimes falls off; when
    this occurs the shell is said to be decollated.

    NUCULA. Lam. (_A small nut._) _Fam._ Arcacea, Bl. and Lam.--_Descr._
    Equivalve, inequilateral, transverse, covered with an epidermis; hinge
    linear, with a series of sharp, angulated teeth, arranged in a line on
    each side of the umbones, and a central ligamentary pit; muscular
    impressions two, simple; palleal impressions not sinuated.--_Obs._ The
    row of teeth on each side of the umbones, and the ligamentary pit in
    the centre of the hinge prevent the pretty little shells of this genus
    from being confounded with any other. Thirty-four figures are
    enumerated in the catalogue by Sowerby, sen. which accompanies the
    Conchological Illustrations of the author. The new species, to the
    amount of 24, have been figured in parts 14 to 16, of the above
    mentioned work. Recent Nuculæ are found from the frozen to the torrid
    zones, and the fossil species occur in nearly all the beds from the
    Pliocene to the Carboniferous system.

    NUMMULACEA. Bl. The third family of Cellulacea, Bl. described as
    containing shells or calcareous bodies, which are characterized as
    discoidal, lenticular; without the slightest traces of whorls to be
    seen externally. The whorls are numerous, internal, and divided into a
    great number of cells, which are separated from each other by
    imperforate septa. This family contains the genera Nummulites,
    Siderolites, Vorticialis, Helicites, Orbiculina, Placentula.

    NUMMULTTES. Lam. (_Nummus_, money.) _Fam._ Nautilacea, Lam.--_Descr._
    Orbicular, convolute, shewing no trace of spire externally; interior
    divided into cells spirally arranged.--_Obs._ The singular fossils
    composing this genus receive their name from their external resemblance
    to a battered coin. Fig. 472. N. lenticulina.

    NUX. Humph. CYCLAS, Lam.

    NYMPHACEA. Lam. A family belonging to the order Conchifera Dimyaria,
    Lam. Ligament external, placed on a prominent fulcrum. This family
    contains the following genera:

        1. SANGUINOLARIA. Rostrated, gaping; two cardinal teeth in each
        valve, including _Soletellina_ and _Lobaria_. Fig. 98, 99.

        2. PSAMMOBIA. Quadrate; valves closed, including Psammotæa. Fig.
        100.

        3. CORBIS. Thick, fimbriated; a cardinal tooth in the centre of a
        pit. Fig. 101.

        4. GRATELOUPIA. A series of small teeth filling a triangular area.
        Fig. 102.

        5. EGERIA. One single and one double cardinal tooth. Fig. 103.

        6. LUCINA. Rounded; anterior muscular impression tongue-shaped.
        Fig. 104.

        7. TELLINA. An anterior fold in the ventral margin; lateral teeth.
        Fig. 105, 106.

        8. TELLINIDES. No anterior fold; no lateral teeth. Fig. 107.

        9. DONAX. Margin denticulated; shell wedge-shaped. Fig. 108.

        10. CAPSA. Margin not denticulated, no lateral teeth. Fig. 109.

    OBELISCUS. Humph. TROCHUS, Lam.

    OBLIQUE. (_obliquus._ lat.) In a slanting direction. The whorls of
    spiral univalves generally take an oblique direction in reference to
    the imaginary axis of the shell. A bivalve is said to be oblique when
    it slants off from the umbones. An example of this is seen in Avicula,
    fig. 163.

    OBSOLETE. (_obsoletus_, lat.) Worn out, out of use. This term is used
    to express an indistinctness of character, which sometimes results from
    the action of sea-water upon unprotected parts of the shell, and
    sometimes from the deposits of enamel formed in age, and covering the
    early striæ, ribs, teeth, &c. thereby rendering them less acute.

    OBTUSE. (_obtusus_, blunt.) The application of this term is not
    peculiar to conchology. It is most frequently used to express the
    character of the spire. _Ex_. The apex of Megaspira, fig. 294.

    OCEANUS. Montf. ("Corne d'ammon vivant," Fr.) NAUTILUS umbilicatus,
    Auct.

    OCTHOSIA. Ranz. CLITIA, Leach.

    OCTOCERA. Bl. The first family of the order Cryptodibranchiata, Bl.
    containing the genus Octopus. A species of which being found in the
    Argonauta, or Paper Sailor, has given rise to the long continued
    controversy as to whether it is really the constructor of the shell, or
    whether it is a mere pirate, and having destroyed the true animal of
    the Argonaut, has possessed itself of the habitation. This question is
    now set at rest. See ARGONAUTA.

    OCTOGONAL. (_octogonum._) Having eight angles. For an example, see
    Dentalium, fig. 2.

    OCTOMERIS. Sow. ([Greek: oktô], _octo_, eight; [Greek: meros], _meros_,
    part.) _Fam._ Balanidea, Bl. _Order_, Sessile Cirripedes,
    Lam.--_Descr._ Eight principal valves circularly arranged, forming a
    compressed cone, attached by a jagged base; aperture enclosed by an
    operculum, consisting of four valves in pairs.--_Obs._ The only genus
    of Sessile Cirripedes agreeing with this in the number of principal
    valves is Catophragmus, Sow. which is, however, sufficiently
    distinguished by the several rows of smaller valves by which the
    principals are surrounded at the base. O. angulosus, fig. 24.

    ODONTIS. Sow. MONODONTA, Lam.

    ODOSTOMIA. Flem. _Descr._ "Shell conical; aperture ovate; peristome
    incomplete, retrally, and furnished with a tooth on the pillar." A
    genus composed of several small species of land shells. Turbo plicatus,
    Spiralis, Unidentatus, &c. Mont.

    OLIVA. Auct. (_An olive._) _Fam._ Convoluta, Lam. Angyostomata.
    Bl.--_Descr._ Oblong, cylindrical, thick, smooth, shining; spire very
    short, with sutures distinct, aperture elongated, notched at both
    extremities; outer lip generally thick; columella thick, obliquely
    striated, terminated by a tumid, oblique, striated varix; a raised band
    passing round the lower part of the body whorl.--_Obs._ The shells
    composing this well known genus present a great variety of rich
    markings and brilliant colours. They are marine and tropical. Fossil
    species are found sparingly in the London Clay and Calcaire-grossièr.
    The Ancillariæ are distinguished from this genus by the sutures of the
    whorls being covered by enamel. O. maura, fig. 457.

    OLIVELLA. Sw. A genus of "Olivinæ," Sw. thus described: "Oliviform;
    spire (typically) rather produced; the tip acute; inner lip not
    thickened; outer lip straight; base of the pillar curved inwards, and
    marked by two strong plaits; upper plaits obsolete or wanting; aperture
    effused at the base only; biplicata, Tank. Cat. 2332. purpurata. Zool.
    Ill. ii. 58. f. 1. mutabilis. _Say._ eburnea. Zool. Ill. ii. 58, f. 2.
    conoidalis. _Lam._ No. 57. oryza. _Lam._ No. 62."

    OLYGYRA. Say. Mentioned by Ranz as properly belonging to Helicina. H.
    neritella, Auct.

    OMALAXIS. Desh. Subsequently BIFRONTIA. Desh. Fig. 354.

    ONISCIA. Sow. (G. B.) _Fam._ Purpurifera, Lam. Entomostomata,
    Bl.--_Descr._ Oblong, sub-ovate, slightly turbinated, cancellated;
    spire short; aperture elongated; terminating anteriorly in a very
    short, recurved canal; outer lip thickened, denticulated within; inner
    lip spread over a portion of the body whorl, granulated.--_Obs._ The
    granulated inner lip is the principal character by which this genus is
    distinguished from Cassidaria. In Oniscia the canal is not so produced.
    O. oniscus, fig. 409.

    ONUSTUS. Humph. A genus proposed by Humphrey and adopted by Swainson
    who describes it thus: "Shell trochiform; the surface irregular, and
    often covered with extraneous bodies, cemented and incorporated with
    the calcareous substance of the shell; the under part of the body whorl
    flattened or concave, umbilicate. O. Solaris. Mart. 173. f. 1700, 1701.
    Indicus. Ib. 172. f. 1697. 1698." It is probable, from the above
    description, that Mr. Swainson intended to include Trochus agglutinans
    of authors. (Genus Phorus, Montf.) Fig. 360.

    OPERCULAR. Of, or belonging to, the operculum. A term applied to the
    valves which compose the operculum of multivalve shells, as
    distinguished from the parietal valves, or those which are arranged
    circularly and form the body of the shell.

    OPERCULINA. D'Orb. A genus of microscopic Foraminifera.

    OPERCULUM. (_A cover or lid._) The plate or plates with which many
    molluscous animals enclose the aperture of their shells, when retired
    within them. The operculum is sometimes horny, as in Trochus;
    testaceous or shelly, as in Turbo. It is spiral when from a central or
    sub-central nucleus, the successive layers take a revolving direction,
    as in Trochus. It is concentric or annular when the outside edge of
    each layer entirely surrounds the preceding one. It is unguiculated,
    when the laminæ are placed side by side, as in Purpura. The opercula of
    multivalve shells are composed of two or four pieces, which are called
    the opercular valves. The shelly or membranaceous plate with which some
    of the animals enclose the aperture of their shells, during the wintry
    part of the year, for the purpose of protecting them while in a torpid
    state, and which they get rid of by dissolving the edges, when
    preparing to emerge from their temporary retirement, must not be
    considered as the operculum, as it does not belong to or form part of
    either the animal or its shell, but is produced for the occasion by a
    secretion of the animal, being deposited in a soft state and
    subsequently hardening. It is called the epiphragm, and may easily be
    distinguished from the true operculum by the texture, and by the
    circumstance of their being soldered to the edge of the aperture. The
    operculum, on the contrary, is moveable, and is always composed of a
    series of successive layers, corresponding with the growth of the
    shell.

    OPIS. Defr. A genus described by De Blainville as consisting of species
    of Trigonia which have the umbones sub-spiral, with a large, striated
    tooth on the hinge. Opis cardissoides, Trigonia, Lam. Opis similis,
    Sow. Min. Con. pl. 232. f. 2.

    ORAL. (_Os_, _oris_, mouth.) Applied to that part of a shell which
    corresponds with the mouth of the animal, but very seldom used in this
    sense.

    ORBICULA. Lam. (_Orbis_, an orb.) _Fam._ Brachiopoda, Lam.
    Palliobranchiata, Bl.--_Descr._ Inequivalve, irregular, sub-orbicular,
    compressed, attached by a fibrous substance passing through a fissure
    near the centre of the lower valve; upper valve patelliform, with the
    umbo central; muscular impressions four in each valve, semilunar. South
    America and West Indies.--_Obs._ Discina, Lam. is an Orbicula. Crania
    is known from this genus by having no fissure in the lower valve, but
    being attached by its substance. Hipponyx has only two muscular
    impressions in each valve. O. lævis, fig. 201.

    ORBICULAR. (_Orbiculus_, a little orb.) Of a round or circular form.

    ORBICULINA. Lam. A genus of microscopic Foraminifera.

    ORBIS. Lea. A minute fossil, described as "orbicular, with flat
    quadrate whorls and aperture square," in other respects resembling
    Solarium. O. Rotella, fig. 355, 356.

    ORBITINA. Risso. A genus said to be established upon the nuclei of two
    land shells.

    ORBULITES. Lam. A genus separated from Ammonites on account of the last
    volution covering the spire. This is generally considered as
    characterizing the Nautili, and distinguishing them from the Ammonites;
    but there are so many gradations that it seems impossible to maintain
    the distinction in this respect. Fig. 479, O. crassus, fig. 480, O.
    discus.

    OREAS. Montf. Part of CRISTELLARIA, Lam. A genus of microscopic
    Foraminifera.

    ORTHIS. Dalman. ([Greek: orthos], _orthos_, straight.) _Fam._
    Brachiopoda, Lam. One of the generic divisions of Brachiopoda by
    Dalman, thus described: "Hinge rectilinear, with umbones distant; the
    larger valve with a transverse, basal, smooth area, with a triangular
    pit." O. basalis, fig. 207.

    ORTHOCERA. Lam. See NODOSARIA.

    ORTHOCERATA. Lam. A family of Polythalamous Cephalopoda, Lam.
    containing the following genera:--

        1. CONULARIA. Conical, externally striated; no siphon. Fig. 469.

        2. AMPLEXUS. Cylindrical; margins of the septa reflected. Fig. 463.

        3. ORTHOCERATITES. Straight, gradually conical; septa simple;
        siphon central. Fig. 464.

        4. NODOSARIA. Divided externally into lobes. Fig. 465.

        5. BELEMNITES. Straight, conical; septa simple; siphon lateral;
        apex solid; internal cast, or nucleus, pyramidal, separable. Fig.
        466 to 468.

        6. CONILITES. Like Belemnites, but external shell thin at the apex.
        Fig. 470.

    ORTHOCERATA. Bl. The first family of Polythalamacea, Bl. containing the
    genera Belemnites, Conularia, Conilites, Orthoceras and Baculites. De
    Blainville remarks that the genera included in this family are all
    fossils, and known very imperfectly, in consequence of the greater part
    of the specimens being only casts.

    ORTHOCERATITES. Auct. _Fam._ Orthocerata, Lam. and Bl.--_Descr._
    Straight, conical, divided into numerous chambers by simple septa
    perforated by a central siphon. O. annulata, fig. 464.

    OSTEODESMA. Desh. PERIPLOMA, Schum.

    OSTRACEA. (_Ostracées_, Lam.) A family belonging to the second section
    of the order Conchifera Monomyaria, the shells of which are described
    as irregular, foliaceous, sometimes papyraceous, with the ligament
    wholly or partly interior. The principal difference between the
    Ostracea and the Pectinides consists in the absence of the auricles and
    the foliated structure of the shells, for, although the Spondylus has
    ex-foliations or spines upon the external surface, the shell itself is
    compact and firm. This family contains the genera Gryphæa, Ostrea,
    Vulsella, Placuna, Anomia, which may be thus distinguished:--

        1. PEDUM. Flat, turned up at the sides, an hiatus for the passage
        of a byssus. A triangular disc on the hinge. Fig. 179.

        2. OSTREA. Foliaceous, irregular, hinge on a small triangular disc.
        Including Dendostrea, Ostræa, Exogyra, Gryphæa. Fig. 180 to 183.

        3. PLACUNA. Two diverging ribs near the umbones. Fig. 184.

        4. PLACUNANOMIA. The same, but attached by fibres passing through a
        hole in one valve. Fig. 189 to 191.

        5. ANOMIA. No costæ, attached by a bony substance passing through a
        hole in one valve. Fig. 186 to 188.

        6. VULSELLA. Tongue-shaped, a ligamentary pit on the hinge. Fig.
        185.

        7. MULLERIA. Doubtful. Fig. 192.

    OSTRACEA. Bl. The first family of the order Lamellibranchiata, Bl.
    containing the genera Anomia, Placuna, Harpax, Ostrea (including
    Dendostrea, Sw.) Gryphæa. To these may be added Placunanomia, Brod. and
    Mulleria.

    OSTREA. Auct. ([Greek: ostreon], _ostreon_, a bone.) _Fam._ Ostracea,
    Lam. and Bl.--_Descr._ Irregular, inequivalve, generally inequilateral,
    foliaceous, attached by part of the lower valve; hinge sometimes
    slightly crenated; destitute of teeth; with the ligament spread upon
    the lower part of a central, triangular area, which is divided into
    three parts; upper valve much flatter than the lower; muscular
    impressions one in each valve, large, sub-central, sub-orbicular, with
    one very minute.--_Obs._ The Linnæan Genus Ostrea includes the Pectens
    and many other genera so different from each other that, without any
    desire to increase the number of genera, it was found necessary by
    subsequent authors to separate them. The common Oyster is the type of
    this genus as at present constituted, and is well known to be abundant
    in various parts of the world. Those which depart furthest from this
    type are the Gryphæa, Lam. with a prominent, incurved umbo in the lower
    valve. The Dendostrea, Sw. with margins characterized by strongly
    angulated folds, throws out arms from the lower valve, by which they
    are attached to stems of sea-weed, &c. Fig. 180, O. edulis. Fig. 181,
    O. folium. (Dendostrea, Sw.) Fig. 182, Gryphæa incurva. Fig. 183,
    Exogyra conica.

    OTIDES. Bl. The first order of Scutibranchiata, Bl. containing the
    genera Haliotis and Ancylus.

    OTION. Leach. ([Greek: ôtion], a little ear.) _Order._ Pedunculated
    Cirripedes, Lam.--_Descr._ Body sub-quadrate, supported on a fleshy
    pedicle with a gaping aperture and two posterior auricular tubes;
    valves five, separate, two semilunar, placed at the sides of the
    aperture, two terminal, very small, one dorsal, minute.--_Obs._ Otion
    differs from Cineras in having two cylindrical posterior tubes, and in
    the extreme minuteness of three out of five of the valves. Found on
    spars floating in the sea, &c. O. Cuvierii, (Lepas aurita, Linn.) Fig.
    43, O. Cuvieri.

    OTIS. Humph. AURICULA, Lam.

    OVATE. (_Ovatus._) Egg-shaped or oval.

    OVEOLITHES. Montf. A microscopic shell resembling Bulla.

    OVIPAROUS MOLLUSCA. Those which produce their young in eggs. Used in
    distinction from the VIVIPAROUS MOLLUSCA, whose young are perfectly
    formed before they leave the body of the parent.

    OUTER LIP. See LABRUM.

    OVULUM. Brug. (_Ovum_, an egg, dim.) _Fam._ Convoluta, Lam.
    Angyostomata, Bl.--_Descr._ Ovate or fusiform, smooth, convolute, spire
    covered; aperture narrow, with a canal at each extremity; outer lip
    crenulated, inflected; inner lip smooth, callous towards the spiral
    extremity; dorsal area wide, sometimes indistinctly marked.--_Obs._ The
    Ovula were placed by Linnæus in his genus Bulla, from which they are
    very remote. They differ from Cypræa in having the inner lip smooth. We
    have given representations of their different forms as follows: O.
    Ovum, fig. 442. O. verrucosum, (Calpurnus Montf.) fig. 441. O. Volva,
    the weaver's shuttle (Radius, Montf.) fig. 442. O. gibbosum, (Ultimus,
    Montf.) fig. 443.

    OXYSTOMATA. Bl. The fifth family of Asiphonibranchiata, Bl. This family
    appears to have been formed for the express purpose of providing a
    place in the system for the genus Janthina, which seems to bear so
    little analogy with other genera of Mollusca, that conchological
    writers have been puzzled to know where to place it.

    PACHYLABRA. Sw. PACHYSTOMA, Guild. A sub-genus of Ampullaria, the outer
    lip of which is thickened within. _Ex._ Ampullaria globosa.

    PACHYMYA. Sow. ([Greek: pachus], _pachus_, thick, and _Mya_.) _Fam._
    Cardiacea? Lam.--_Descr._ Obliquely elongated, equivalve, thick,
    sub-bilobed, with beaks near the anterior extremity; ligament partly
    immersed attached to prominent fulcra.--_Obs._ This singular fossil is
    shaped like Modiola, but the shell being extremely thick, and the
    ligament attached to a prominent fulcrum, it is difficult to know where
    to place it. Fig. 130, Pachymya Gigas.

    PACHYSTOMA. Guild. ([Greek: pachus], _pachus_, thick; [Greek: stoma],
    _stoma_, mouth.) A genus composed of such species of Ampullaria, Auct.
    as have the edge of the aperture thickened and grooved within so as to
    form a sort of ledge upon which the operculum rests. Ampullaria globosa
    and corrugata are examples of this variation. The name Pachylabra is
    given to such species by Swainson, who objects to the above name on
    account of its having been previously used to a genus of fishes. Fig.
    539.

    PACHYTOMA. Sw. A sub-genus of Helicina, thus described, "Aperture
    entire; the inner lip very thick; the spiral whorls hardly convex; P.
    occidentalis. Zool. J. iii. 15. f. 6-10. viridis, Zool. Journ. i. pl.
    6. f. 7." Sw. p. 337.

    PACLITES. Montf. A genus composed of species of Belemnites, Auct.
    described towards the extremity, with a pore, at the apex, and a
    straight lengthened aperture. _Ex._ B. ungulatus, Bl.

    PADOLLUS. Montf. A genus composed of species of HALIOTIS, with a
    strongly marked spiral groove. _Ex._ H. tricostalis, Lam. Fig. 339.

    PAGODELLA. Sw. A sub-genus of Trochus, thus described: "Trochiform;
    generally thin, and always not pearlaceous; aperture and pillar
    perfectly united and entire; operculum horny. P. major. Mart. 163. f.
    1541, 1542. tectum-persicum. Ib. f. 1543, 1544." Sw. p. 351.

    PALLEAL IMPRESSION. (_Pallium_, a mantle.) The mark or groove formed in
    a bivalve shell by the muscular attachment of the mantle, which, being
    always found near the margin of the shell, is sometimes termed the
    marginal impression. In bivalves with two muscular impressions it
    passes from one to the other. If in passing, it takes a bend inwards
    posteriorly, it is said to be sinuated, and that part is called by Mr.
    Gray, the Siphonal scar.

    PALLIOBRANCHIATA. Bl. The first order of the class Acephalophora. Bl.
    The animals of this order are described as more or less compressed,
    included between the two valves of a bivalve shell, one inferior, the
    other superior, joining at the back and opening in front. The
    Palliobranchiata in the system of De Blainville correspond with the
    Brachiopoda in the system of Lamarck, and the shells may be known by
    their being symmetrical. This order contains in the first section of
    symmetrical bivalves, Lingula, Terebratula, Thecidium, Strophomena,
    Plagiostoma, Dianchora and Podopsis: in the second section, Orbicula
    and Crania.

    PALMATED. Flattened like a palm, as the fronds or fringes of some
    Murices.

    PALMINA. Gray. Differing from OTION in having but one auricle.

    PALUDINA. Lam. _Fam._ Peristomata, Lam. Cricostomata, Bl--_Descr._
    Varying in form from oval to globose, in some instances oblong, covered
    with a greenish horny epidermis; spire acute, composed of rounded
    whorls; aperture ovate; peritreme entire, slightly modified by the last
    whorl; operculum horny, concentric. Europe, North America, East Indies,
    China, &c.--_Obs._ The construction of the operculum distinguishes this
    genus of freshwater shells from Valvata and Cyclostoma. The Paludinæ
    are viviparous. Fig. 321. P. Achatina.

    PALUDOMUS. Sw. A genus of the family of "Melanianæ," Sw. described as
    differing from Melania in having the spire shorter than the aperture.
    Sw. p. 340.

    PANDORA. Brug. _Fam._ Corbulacea, Lam. Pyloridea, Bl.--_Descr._ Thin,
    inequivalve, pearly within, rounded anteriorly, rostrated posteriorly;
    right valve flat with a cardinal tooth, or short rib, and a slit
    containing the cartilage with a narrow plate on the dorsal edge turned
    towards the left valve; left valve concave, with a receptacle for the
    cardinal tooth of the right valve and the internal cartilage; no
    external ligament. Europe, America, Ceylon, &c.--_Obs._ This well known
    genus is in no danger of being confounded with any other shell. Fig.
    90. P. rostrata.

    PANOPÆA. Menard. _Fam._ Solenacea, Lam. Pyloridea, Bl.--_Descr._
    Equivalve, inequilateral, oval, gaping at both extremities; hinge with
    an acute cardinal tooth in each valve, and a large callosity near the
    umbones supporting the ligament; muscular impressions two, distant,
    oval; palleal impression with a large sinus. Britain, North America,
    Mediterranean, Australia, &c.--_Obs._ This genus resembles Mya in
    general appearance, but differs in having an external ligament and a
    sharp tooth, instead of the broad spoon-shaped process in the hinge of
    the latter genus. Fig. 65. P. Australis.

    PAPER SAILOR. A common name given to the Argonauta.

    PAPILLARY. (_Papilla_, a teat.) Shaped like a teat. This term is
    applied by conchologists when the apex of the spire of an univalve
    shell is rounded like a teat and not spiral up to the extreme point; as
    the apex of Cymba, fig. 434.

    PAPYRACEOUS. (_Papyrus_, a kind of paper made of the flags of the river
    Nile in Egypt.) Of a thin, light texture, resembling that of paper. An
    example of this is to be seen in the Argonauta, commonly called the
    "Paper Sailor," fig. 485, and in the Pholas papyracea, fig. 56.

    PAPYRIDEA. Sw. A sub-genus of Cardium, thus described; "Shell
    heart-shaped, or transversely oval; inequilateral; the anterior side
    almost always gaping; representing the Pholidæ. P. Soleniforme, Wood,
    Conch. pl. 56. f. 3.--apertum, Ib. 56. f. 2.--transversum, Sow. Conch.
    f. 4.--ringens, Wood, pl. 53. f. 1, 2."

    PARACEPHALOPHORA. Bl. The second class of the type Malacozoa, Bl.
    divided into the sub-classes: P. dioica, P. monoica, P. hermaphrodita.

    PARIES. (_A wall._) The principal part of a multivalve shell, forming a
    circular wall round the body of the animal, and composed of one or more
    valves which are called the parietal valves.

    PARIETAL VALVES. The principal valves of multivalve shells surrounding
    the body like a wall; as distinguished from the opercular valves, or
    those which compose the operculum.

    PARMACELLA. Cuv. (_A little cell._) _Fam._ Limacinea, Lam. and
    Bl.--_Descr._ Haliotoid, internal, thin; spire flat, consisting of one
    or two rapidly increasing whorls; aperture as large as the whole shell,
    with the dorsal margins inflected.--_Obs._ This description applies to
    Parmacella of Cuvier. The shell figured in Sowerby's Genera under that
    name is Cryptella of Webb. Fig. 257, P. Olivieri. Fig. 258, P.
    Palliolum.

    PARMOPHORUS. Bl. A genus composed of EMARGINULA elongata, Auct. and
    other species of a similarly elongated form. Australian. Fig. 242. P.
    elongatus.

    PARTULA. Fer. _Fam._ Colimacea, Lam. Auriculacea, Fer.--_Descr._
    Conical, smooth; spire equal to the aperture in length, consisting of
    few whorls; aperture auriform; outer lip reflected, broad; inner lip
    reflected, with a slight prominence on the columella. P. australis,
    fig. 302.

    PASITHÆA. Lea. A genus formed of some pyramidal shells, described as
    resembling Melania, but separated from that genus on account of being
    marine fossils. Fig. 317, P. striata.

    PATELLA. Auct. (_A dish_ or _platter_.) _Fam._ Phyllidiana, Lam.
    Retifera, Bl.--_Descr._ Symmetrical, compresso-conical, nearly regular,
    oblong or oval; apex sub-central, inclining towards the anterior
    margin; aperture oval, forming the base of the shell; internal surface
    smooth; with a muscular impression shaped like a horse-shoe, with the
    ends bending forwards, encircling and dividing the space all round,
    except where the interruption occurs to receive the head of the animal;
    external surface ribbed, grooved, striated or banded radiately. On
    rocks and sea-weeds in all climates.--_Obs._ Patelloida differs from
    Patella in the construction of the animal; Siphonaria, in the lateral
    siphon; and Ancylus, in the oblique twist of the axis, as well as in
    the nature of the animal. The Patellæ are marine. Fig. 229, P. Oculus.

    PATELLIFORM. (_Patella_, a dish; _forma_, shape.) Shaped like a dish,
    or like shells of the genus Patella.

    PATELLOIDA. Quoy and Gaimard. LOTTIA, Gray.--_Fam._ Phyllidiana,
    Lam.--_Descr._ Patelliform, rather flat; apex obtuse, leaning towards
    the posterior margin; muscular impression not symmetrical, but widest
    on the right side near the head of the animal; central disc of a
    variable brown colour. On rocks and sea-weeds in all climates.--_Obs._
    The shells of this genus so closely resemble Patella that it is almost
    impossible to make the distinction from the shells alone. They are,
    however, generally flatter, and have the apex placed somewhat nearer
    the posterior margin. The animals are very distinct. Fig. 231, P.
    Antillarum.

    PATELLOIDEA, Bl. or patelliform shells. The third family of the order
    Monopleurobranchiata, Bl.; the animals of which are described as
    depressed, flattened, covered by a wide external shell, which is
    patelliform and non-symmetrical. This family contains the genera
    Umbrella and Siphonaria.

    PATROCLES. Montf. A genus of microscopic Foraminifera.

    PATULARIA. Sw. A sub-genus of "Anodontinæ," Sw. thus described: "Shell
    nearly equilateral, round or cordate; no teeth. P. ovata, Sw." _Ex._
    _Conch._ pl. 36. rotundatus, Ib. pl. 137.

    PAVONIA. D'Orb. A genus of microscopic Foraminifera.

    PAXYODON. Schum. HYRIA, Lam.

    PECTEN. Brug. (_A comb._) _Fam._ Pectenides, Lam. Subostracea,
    Bl.--_Descr._ Inequivalve, ribbed longitudinally, nearly equilateral,
    with a triangular auricle on each side of the umbones; hinge linear,
    destitute of teeth, having a central pit containing the cartilage;
    muscular impressions one in each valve, large, sub-central.--_Obs._
    This genus of beautiful shells, to which the well known Scallop
    belongs, contains numerous species, some of which are found in the
    British Seas. The Hinnites Pusio (P. Pusio of some authors) has been
    separated on account of the irregularity of the external surface of one
    valve. Fig. 171 to 173.

    PECTENIDES. Lam. A family belonging to the second section of the order
    Conchifera Dimyaria, Lam. including the following genera.

        1. PECTEN. Unattached, including _Decatopecten_ and _Hinnites_.
        Fig. 171, 172, 173.

        2. LIMA. Unattached, gaping, Fig. 174.

        3. PLAGIOSTOMA. Unattached, with an area between the umbones. Fig.
        176.

        4. DIANCHORA. Attached by the point of the umbo. Fig. 175.

        5. SPONDYLUS. Attached, irregular, a triangular area in one valve,
        divided by a slit. Fig. 177.

        6. PLICATULA. Plicated, a very small area in one valve. Fig. 178.

    PECTINATED. (_Pecten_, a comb.) Marked in a regular series of ridges.

    PECTUNCULUS. (_Pecten_, dim.) _Fam._ Arcacea, Lam. and Bl.--_Descr._
    Equivalve, sub-equilateral, orbicular, thick, covered with a velvety
    epidermis, striated longitudinally; ventral margin denticulated within;
    hinge semi-circular, with a series of small teeth on each side of the
    umbones, which are separated by a small triangular disc in each valve
    bearing the ligament; muscular impressions two in each valve, strongly
    marked, united by an entire palleal impression.--_Obs._ Linnæan
    conchologists have mixed this genus with Arca, from which it is,
    however, totally distinct, not only in the roundness of the general
    form, but also, and principally, in the curve of the hinge line; in
    fact the characters of this genus are so strongly marked that there is
    no danger of confounding it with any other. It does not contain many
    species; two or three are British. The fossil species occur in London
    Clay and Calcaire-grossiér. Fig. 134, P. pilosus.

    PEDICLE or PEDUNCLE. (_Pedunculus_, a little foot.) The stem or organ
    of attachment of the class of shells called in the system of Lamarck
    "Pedunculated Cirripedes," consisting of a fleshy tendinous tube, by
    the lower end of which they are attached to sub-marine substances.

    PEDICULARIA. Sw. A genus of "Scutibranchia," thus described: "Shell
    irregular, sub-patelliform; a thick, large, obsolete apex on one of the
    longest sides, and an internal callous rim within, on one side only;
    circumference undulated, irregular. P. Sicula, Sw." Sw. p. 357. Sicily.
    A singular shell of the nature of Calyptræa, which is found attached to
    corals, conforming its shape to the irregularity of their surface, and
    fitting closely. _Ex._ Fig. 513.

    PEDIPES. Adanson. _Fam._ Auriculacea, Bl. Colimacea, Lam.--_Descr._
    Sub-globose, longitudinal, thick, striated; spire equal to the aperture
    in length; aperture sub-ovate; peritreme sharp, thickened within,
    modified by the last whorl; columella with three strong plaits on the
    inner edge; outer lip with one fold.--_Obs._ This genus contains but
    one or two small recent species, which in some respects resemble
    Auricula, from which it is known by the thickness of its shell, and its
    globular form. Fig. 299, P. Adansoni. Coast of Africa.

    PEDUM. Lam. (_A shepherd's crook._) _Fam._ Pectinides, Lam.
    Sub-ostracea, Bl.--_Descr._ Irregular, inequivalve, sub-equilateral,
    attached by a byssus passing through a sinus in the lower valve; hinge
    toothless, with a triangular area in each valve, separating the
    umbones; ligament contained in a groove running across the area;
    muscular impressions one in each valve, large, sub-orbicular; both
    valves flat, narrow at the dorsal, broad at the ventral extremities;
    lower valve with raised edges overwrapping the upper.--_Obs._ This
    singular genus, of which only one species is known, differs from
    Ostrea, not only in shape and structure, but also in the mode of
    attachment, which is by means of a byssus passing through the lower
    valve, in Pedum, but by a portion of the outer surface of the shell in
    Ostrea. P. Spondyloideum (fig. 179) is the only species at present
    known. Moluccas.

    PEDUNCLE. See PEDICLE.

    PEDUNCULATED. (_Pedunculus_, a little foot.) Attached to external
    objects by a hollow fleshy tube, called the Peduncle.

    PEDUNCULATED CIRRIPEDES. Lam. An order consisting of molluscs which
    have multivalve shells, supported on a peduncle. The genera which it
    contains are thus distinguished:

        1. PENTELASMIS. Five valves. Fig. 34.

        2. CINERAS. Five very minute valves distant from each other. Fig.
        42.

        3. OTION. The same, but the animal has two auricles. Fig. 43. The
        genus Palmina, Gray, has but one.

        4. OCTOLASMIS. Shaped like Pentelasmis, but with 7 or 8 valves.
        Fig. 41.

        5. LITHOTRYA. Five valves, peduncle scaly with a plate at the base.
        Fig. 39.

        6. SCALPELLUM. Shape square, valves 13, peduncle scaly. Fig. 35.

        7. SMILIUM. Same, but the peduncle hairy. Fig. 36.

        8. IBLA. Four valves, one pair long, one pair short, peduncle
        hairy. Fig. 40.

        9. BRISMEUS. Seven valves, even at the base. Fig. 38.

        10. POLLICIPES. Principal valves in pairs, with many smaller valves
        at the base. This genus has been divided into _Pollicipes_, and
        _Capitellum_, the latter of which is founded upon Pollicipes
        Mitellus, Auct. Fig. 37 and 37*.

    PELAGUS. Montf. A genus composed of species of AMMONITES, which have
    the spire covered by the last whorl, as in Nautilus and have an
    umbilicus. ORBULITES. Bl.

    PELLUCID. Transparent.

    PELORUS. Montf. POLYSTOMELLA, Bl. A genus of microscopic Foraminifera.

    PELORONTA. Oken. NERITA _Peloronta_, Auct. Fig. 330.

    PENEROPLIS. Montf. A genus of microscopic Foraminifera.

    PENICILLUS. Brug. ASPERGILLUM, Auct.

    PENTALEPAS. Bl. PENTELASMIS, Auct.

    PENTAMERUS. Sow. ([Greek: Pente], _pente_, five; [Greek: meros],
    _meros_, part.) _Fam._ Brachiopoda, Lam.--_Descr._ Equilateral,
    inequivalve; one valve divided by a central septum into two parts; the
    other by two septa, into three parts; umbones incurved,
    imperforate.--_Obs._ Dalman remarks upon his genus Gypidia, that it is
    most probably identical with PENTAMERUS, Sow. but rejects the name for
    two reasons; 1st. That it has already been applied to a class of
    insects; 2nd. He disputes the fact of the shell being quinquelocular,
    i.e. not counting the triangular foramen in the hinge of the larger
    valve as one of the divisions. Fig. 212, 213.

    PENTELASMIS. Leach. ([Greek: pente], _pente_, five; [Greek: elasma],
    _elasma_, plate.) _Order._ Pedunculated Cirripedes, Lam.--_Descr._
    Compressed, conical, composed of five valves; lower lateral pair
    sub-trigonal; upper lateral pair elongated, sub-quadrate; dorsal valve
    arcuate, peduncle elongated, smooth. Found on floating wood in the
    sea.--_Obs._ This genus is known from all others of the order by the
    number of valves. Pentelasmis is the genus Anatifera of Lamarck. Lepas
    anatifer, Linn. Fossil species of this marine genus are found in the
    Calcaire-grossièr of Paris, and in other similar beds. Fig. 34, P.
    lævis.

    PENULTIMATE WHORL. The last whorl but one.

    PERA. Leach. A genus composed of CYCLAS amnica, and other similar
    species.

    PERDIX. Montf. DOLIUM _Perdix_, Auct.

    PERFORATED. (_Perforatus._) Bored through, as the apex of Fissurella,
    fig. 245, and Dentalium, fig. 2.

    PERFORATION. (_Perforo_, to bore, or pierce.) A round opening, having
    the appearance of being bored, as in Haliotis, fig. 338. Sometimes the
    term is applied to an umbilicus which penetrates a shell through the
    axis to the apex, as Eulima splendidula, fig. 348.

    PERIBOLUS. Brug. A genus founded upon young specimens of CYPRÆA, with
    their outer lips not formed.

    PERIOSTRACUM. A name used by Mr. Gray to signify the substance which
    covers the outer surface of many shells, called the _Epidermis_ by most
    conchological writers. "Drap Marin" is the name given to this substance
    by French Naturalists.

    PERIPLOMA. Schum. _Fam._ Myariæ. A genus thus described: "Shell very
    thin with the left valve more ventricose than the right; hinge
    toothless, ligament double, the external portion thin, the internal
    part thick, placed upon prominent, sometimes spoon-shaped hinge laminæ,
    and supported by a transverse bone; muscular impressions two, distant,
    palleal impression sinuated posteriorly." _Ex._ P. inæquivalvis. fig.
    72. _Genus_, Osteodesma, Deshayes.

    PERISTOMATA. Lam. A family belonging to the first section of the order
    Trachelipoda, containing the following genera:--

        1. AMPULLARIA. Globose or discoidal; operculum concentric;
        including _Pachystoma_, _Lanistes_, _Ceratodes_. Fig. 318 to 320.

        2. PALUDINA. Oval; operculum concentric. Fig. 321.

        3. VALVATA. Globose; operculum spiral. Fig. 322.

    PERISTOME. The edge of the aperture, including the inner and outer
    lips.

    PERITREME. A term used to express the whole circumference of the
    aperture of a spiral shell. It is said to be notched or entire, simple,
    reflected, round or oval, &c.

    PERLAMATER. Schum. (_Mother of Pearl._) MELEAGRINA Margaritifera, Lam.
    The pearl oyster.

    PERNA. Auct. ("Pernæ concharum generis," Plin.) _Fam._ Malleacea,
    Lam.--_Descr._ Sub-equivalve, irregular, compressed, foliaceous; hinge
    straight, linear, composed of a series of transverse, parallel grooves,
    containing the cartilage and intermediate spaces bearing the ligament;
    anterior margin with a sinus for the passage of a byssus; posterior
    ventral margin oblique, attenuated. _Obs._ This genus is known from
    Crenatula by the straightness, number and regularity of the grooves in
    the hinge and the sinus, for the passage of the byssus. Fig. 166, P.
    Ephippium. Mostly tropical.

    PERSICULA. Schum. A genus formed of MARGINELLA _Persicula_, Auct. and
    other species having the spire concealed. Fig. 438.

    PERSONA. Montf. (_Mask_). A genus composed of TRITON _Anus_, Auct. and
    similar species. Fig. 401.

    PETRICOLA. Lam. (_Petrus_, a stone; _cola_, an inhabitant.) _Fam._
    Lithophagidæ, Lam.--_Descr._ Equivalve, inequilateral, transversely
    ovate or oblong, rather irregular, anterior side rounded; posterior
    side more or less attenuated, slightly gaping; hinge with two cardinal
    teeth in each valve; muscular impressions two in each valve; palleal
    impression entire; ligament external.--_Obs._ The Petricolæ are found
    in holes made by the animals in rocks, madrepores, &c. They may be
    known from Saxicava by the regularity of their form and the teeth on
    the hinge. Fig. 91, 92.

    PETRIFIED FINGERS, CANDLES, SPECTRE CANDLES, &c. are vulgar terms by
    which fossils of the genus Belemnites were formerly known.

    PHAKELLOPLEURA. Guild. A genus composed of those species of CHITON,
    Auct. which have bunches of hairs or hyaline bristles on each side of
    each valve on the margin. The Chiton fascicularis, found on our own
    coasts, is a well known example. Fig. 506.

    PHARAMUS. Montf. LENTICULINA, Bl. A genus of microscopic Foraminifera.

    PHARETRIUM. König. ([Greek: pharetreôn], _pharetrion_, a
    quiver.)--_Descr._ A testaceous body composed of two conical sheaths,
    one within the other, perforated at the apex, and joined together near
    the oral margin. P. fragile, fig. 3. In describing this genus, which
    appears to be the same as ENTALIS of Defrance, Mr. König expresses the
    supposition that it may probably belong to the class Pteropoda.

    PHASIANELLA. Auct. (_Phasianus_, a pheasant.) _Fam._ Turbinacea, Lam.
    Ellipsostomata, Bl.--_Descr._ Smooth, oval, variegated; aperture
    entire, oval; outer-lip thin; inner-lip thin, spread over a portion of
    the body whorl; columella smooth, rather thickened towards the base;
    operculum horny, spiral within; testaceous, incrassated without.
    Britain, Mediterranean, &c.; the fine large species are Australian.
    Some fossil species are found in the tertiary beds.--_Obs._ The shells
    composing this genus are richly marked with lines and waves of various
    and delicate colours, and if the genus be restricted to those species
    which are smooth, and which have a thick shelly operculum, we may
    regard it as well defined; but there are some spirally-grooved species
    of TURBO, Linn. which, from their oval shape, have been considered as
    belonging to this genus. Such species should not, in our opinion, be
    retained in this genus; they belong to Littorina. P. variegata, fig.
    367.

    PHITIA. Gray. CARYCHIUM, Müller.

    PHOLADARIA. Lam. A family of the order Conchifera Dimyaria, Lam. The
    animals contained in this family live in cavities bored by themselves
    in rocks, wood, &c. They are cylindrical in form. Lamarck here places
    PHOLAS and GASTROCHÆNA, the last of which belongs more properly to the
    family of Tubicolaria, where we have enumerated it. Pholas has been
    divided into _Pholas_, fig. 55, _Martesia_, which has the valves nearly
    closed; and Pholadidæa, fig. 56, which has the cup-shaped extension.
    The genus Pholadomya, fig. 67, has been added, although of doubtful
    character. The genus Galeomma, fig. 58, 59, has also been recently
    added.

    PHOLADIDÆA. Leach. PHOLAS papyracea, Auct. Remarkable for the
    cup-shaped process at the posterior extremity. Fig. 56.

    PHOLADOMYA. Sow. (_Pholas_ and _Mya_.) _Fam._ Pholadaria,
    Lam.--_Descr._ Thin, rather hyaline, equivalve, inequilateral,
    ventricose, posteriorly gaping, elongated, anteriorly short, rounding;
    ventral margin rather gaping; hinge with an elongated pit, and lateral
    plate in each valve; ligament external, short, muscular impressions two
    in each valve, rather indistinct; palleal impression with a large
    sinus.--_Obs._ The only recent species of this genus is from the island
    of Tortola. Several fossil species occur in rocks of the Oolitic
    series. Fig. 57, P. candida.

    PHOLAS. Auct. ([Greek: PHôleô], _pholeo_, to lie hid in a cavity.)
    _Fam._ Pholadaria, Lam. ADESMACEA, Bl.--_Descr._ Transverse, oblong,
    equivalve, inequilateral, imbricated, gaping on both sides, the
    anterior hiatus being generally the largest, although sometimes nearly
    closed, with the dorsal margin surmounted with one or more laminar
    accessary valves; hinge callous, reflected, with a long curved tooth
    protruding from beneath the umbones in each valve.--_Obs._ This genus
    of marine shells, dwelling in holes formed in rocks, wood, &c. is
    easily distinguished from any other nearly allied genus by the curved,
    prominent, rib-like teeth. Fig. 55, P. Dactylus; 56. P. papyracea.

    PHOLEOBIUS. Leach. Part of the genus SAXICAVA, Auct.

    PHONEMUS. Montf. A genus of microscopic Foraminifera.

    PHORUS. Montf. TROCHUS agglutinans, Auct. Remarkable for the adhesion
    of little pebbles, dead shells, &c. to the outer edge of the whorls,
    which are taken up in the course of the growth of the shell. From this
    circumstance they are called "Collectors, Carriers, &c." Fig. 360.
    Recent species are brought from the East and West Indies; fossil
    species are found in the Tertiary beds.

    PHOS. Montf. _Fam._ Purpurifera? Lam.--_Descr._ Turrited, thick,
    cancellated, varicose; spire pointed, generally longer than the
    aperture; aperture rounded or oval; outer lip having internal ridges,
    with a sinus near the anterior termination; columella with an oblique
    fold; canal short, forming externally a raised varix.--_Obs._ The
    raised external surface of the canal, brings this genus near to
    Buccinum, while, in general appearance, most of the species more nearly
    resemble Murex. They have, however, no true varices on the whorls, but
    merely raised bars. Fig. 416, P. senticosus.

    PHYLLIDIANA. Lam. A family belonging to the first section of the order
    Gasteropoda, Lam. The genera belonging to this family may be
    distinguished as follows:

        1. CHITON. Composed of eight valves; valves contingent. Fig. 227.

        2. CHITONELLUS. The same, with the valves distant. Fig. 228.

        3. PATELLA. Conical, symmetrical. Fig. 229, 230.

        4. PATELLOIDA. Differing from Patella in the animal. Fig. 231.

        5. SIPHONARIA. With a siphon on one side. Fig. 231*.

        6. SCUTELLA. Siphon close to the side of the head. Fig. 510, 511.

    PHYLLONOTUS. Sw. A sub-genus of Murex, thus described: "Canal moderate;
    varices foliated, laciniated, compressed, or resembling leaves;
    inflatus. Mart. 102. fig. 980, eurystoma. Zool. Ill. ii. 100.
    imperialis. Ib. pl. 109." Sw. p. 296.

    PHYSA. Drap. A genus formed for reversed species of Limnæa, Auct. Fig.
    310, P. castanea.

    PHYSETER. Humph. SOLARIUM, Lam.

    PILEOLUS. Cookson. (_A little cap._) _Fam._ Neritacea, Lam.--_Descr._
    Patelliform, with the apex sub-central, straight. In the lower disc, or
    under surface, the centre of which is rather raised or cushion-shaped,
    is placed the lateral, narrow, semilunar aperture, with the outer lip
    marginated and the inner lip crenulated.--_Obs._ This interesting genus
    is known only in a fossil state. Two species are found in the upper
    layer of Oolite, above the Bradford clay. The spire, although internal,
    connects this genus in some degree with Neritina. Still there is no
    danger of confounding them. Fig. 332, P. plicatus.

    PILEOPSIS. Lam. CAPULUS, Montf.

    PILLAR. The usual English name for the column which forms the axis of
    spiral shells, around which the whorls revolve. See COLUMELLA.

    PINNA. Auct. (_The fin of a fish._) _Fam._ Mytilacea, Lam.--_Descr._
    Equivalve, inequilateral, oblique, wedge-shaped, thin, horny; umbones
    terminal; hinge rectilinear, without teeth; anterior margin sinuated,
    to admit the passage of a byssus; posterior margin truncated, gaping;
    muscular impressions two in each valve; posterior large, sub-central;
    anterior small, terminal, sometimes double.--_Obs._ The beautiful large
    shells of which this genus is composed, are possessed of a large,
    flowing, silky byssus, of which gloves and hose have been manufactured.
    They have received their name from their resemblance to the pectoral
    fins of some fishes. Some species attain very large dimensions, and
    measure two feet in length. A very improbable story is told with regard
    to animals of this genus, namely that a certain small species of crab
    is in the habit of taking refuge from its enemies in the shell of the
    Pinna, into which it is received with great hospitality and kindness by
    the "_blind slug_," which inhabits it. In return for which kindness, he
    occasionally goes abroad to procure food for both. On his return he
    knocks at the shell, which is opened to receive him, and they share the
    supplies together in convivial security! Some species are smooth,
    although the greater number are imbricated or crisped outside. P.
    saccata, fig. 162.

    PINNATED. (From _Pinna_, a fin.) When a part of a shell is spread out
    and smooth, as in Rostellaria columbaria, fig. 403, it is said to be
    _alated_, or winged, but when the part which is spread is radiated or
    ribbed, like the fin of a fish, it is _pinnated_, as in Murex pinnatus,
    and Murex tripterus. (Conch. Illustr.)

    PIRENA. Lam. A genus of fresh-water shells, rejected by De Ferussac and
    other authors, who place Lamarck's two first species with Melanopsis,
    and his two last with Melania. Fig. 316, P. terebralis.

    PISIDIUM. Leach. A genus of river shells separated from Cyclas
    principally on account of a difference in the animal. The species of
    Pisidium, however, are less equilateral than the Cyclades, and the
    posterior or ligamentary side of the latter is the longer, while that
    of the former is the shorter. Fig. 112.

    PISIFORM. (_Pisum_, a pea; _forma_, shape.) Shaped like a pea or small
    globular body.

    PISUM. Megerle. (_A pea._) PISIDIUM, Leach.

    PITHOHELIX. Sw. A sub-genus of "Geotrochus," Sw. Sw. p. 332.

    PITONELLUS. Montf. ROTELLA, Auct.

    PLACENTA. Schum. PLACUNA, Auct.

    PLACENTULA. Schum. A genus of microscopic Foraminifera.

    PLACUNA. Brug. ([Greek: plakous], _placos_, a cake.) _Fam._ Ostracea,
    Lam. and Bl.--_Descr._ Compressed, thin, equivalve, nearly equilateral,
    planorbicular, fibrous, foliaceous; hinge flat, with two diverging ribs
    in one valve, and two corresponding grooves in the other, containing
    the cartilage; muscular impressions one, large, circular, central, and
    one or two smaller in each valve.--_Obs._ The two best known species of
    this well defined genus are the P. Placenta, commonly called the
    Chinese Window Shell, and the P. Sella, called the Saddle Oyster, from
    the anterior margin being turned up so as to resemble a saddle. The
    genus may be known from all others by the diverging costa on the hinge.
    Placunanomia is the only genus resembling it in this respect, but this
    is easily distinguished by a perforation through the shell. Fig. 184,
    P. Placuna. These shells are used in China to glaze windows.

    PLACUNANOMIA. (Sw. _Placuna_ and _Anomia_.) _Fam._ Ostracea, Lam. and
    Bl.--_Descr._ Thin, foliaceous, compressed, sub-equivalve,
    sub-equilateral, irregular, flat near the umbones, plicated towards the
    margins, attached by a bony substance passing through a fissure in the
    lower valve; hinge flat, with two diverging ribs in one valve,
    corresponding with two diverging grooves, containing the cartilage, in
    the other; muscular impressions one in each valve, central,
    sub-orbicular.--_Obs._ The specimens from which Mr. Broderip described
    this singular genus, were brought by Mr. Cuming from the gulf of Dulce
    in Costa Rico. Another species is from one of the Philippine Islands.
    They partake of the characters of several genera, having the hinge of
    Placuna, and being attached by a process passing through the lower
    valve, like Anomia. P. Cumingii, fig. 189.

    PLAGIOSTOMA. Sow. Min. Con. ([Greek: plagios], _plagios_, oblique;
    [Greek: stoma], _stoma_, mouth.) _Fam._ Pectenides, Lam.
    Palliobranchiata, Bl.--_Descr._ Sub-equivalve, inequilateral, oblique,
    auriculated on each side of the umbones, radiately striated; hinge
    straight in one valve, with a triangular notch in the other.--_Obs._
    This genus, one species of which is spinous, and another smooth, is
    only known in a fossil state. It is found in the Lias and chalk. Fig.
    176, P. spinosum.

    PLAIT or FOLD. A term applied to the prominences on the columellar lip
    of some univalve shells, particularly in the sub-family of Volutidæ.
    _Ex._ Voluta, fig. 433; Cymba, 434; and Melo, fig. 435.

    PLANARIA. Brown. A minute fossil resembling Planorbis in appearance,
    but differing in being a marine shell, and having a reflected outer
    lip. P. nitens, fig. 312, from Lea's Contributions to Geology.

    PLANAXIS. Lam. (_Plana_, flat; and _axis_.) _Fam._ Turbinacea, Lam.
    Entomostomata, Bl.--_Descr._ Sub-ovate, pyramidal, solid; spire
    measuring ½ or 1/3 of the axis, consisting of few whorls; columella
    contiguous to the axis, flat, truncated, and separated from the outer
    lip by a short canal; outer lip thickened and denticulated within;
    operculum horny, thin, with a terminal nucleus.--_Obs._ This is a genus
    of small marine shells found in the West Indies, &c. Fig. 365, P.
    sulcata.

    PLANE. (_Planus._) Flat, planed, as the columellar lip of Purpura, fig.
    414.

    PLANORBICULAR, (_Planus_, flat; _orbis_, an orb.) Flat and circular, as
    Ammonites, fig. 478.

    PLANORBIS. Müll. (_Planus_, flat; _orbis_, an orb.) _Fam._ Lymnacea,
    Lam. and Bl.--_Descr._ Thin, horny, convolute, planorbicular, nearly
    symmetrical; spire compressed, concave, consisting of numerous
    gradually increasing whorls, which are visible on both sides; aperture
    transversely oval, or nearly round; peritreme entire; outer lip thin;
    inner lip distinct, spread over a part of the body whorl.--_Obs._ This
    is a genus of shells abounding in all climates in ditches and stagnant
    pools, not liable to be confounded with any other, excepting the
    discoidal species of Ampullaria, which may be distinguished by the
    aperture being broadest in the opposite direction. It is further to be
    remarked that the discoidal Ampullariæ are dextral shells, and the
    Planorbes are sinistral or reversed; and although the latter are
    sometimes so flat and orbicular that it is difficult to know which is
    the spiral side, it may nevertheless always be ascertained by a careful
    examination. Fossil species are found in the freshwater strata of the
    Isle of Wight, and the neighbourhood of Paris. Fig. 311, P. corneus.

    PLANORBULINA. D'Orb. A genus of microscopic Foraminifera.

    PLANULACEA. Bl. The second family of Cellulacea, Bl. The microscopic
    Foraminifera contained in this family are described as very much
    depressed, not spiral, chambered, cellular, and having the septa
    indicated by grooves on the external surface of the shell, which
    increase in length from the apex to the base: some of the small
    cellular cavities are to be seen on the margins. This family contains
    the genera Renulina and Peneroplis.

    PLANULARIA. Defr. PENEROPLIS, Montf. A genus of microscopic
    Foraminifera.

    PLANULINA. D'Orb. A genus of microscopic Foraminifera.

    PLANULITES. Lam. DISCORBITES of the same author. A genus of microscopic
    Foraminifera.

    PLATIRIS. Lea. ([Greek: platus], _platus_, wide; [Greek: iris],
    _iris_.) A genus including several species of Nayades, referred to
    IRIDINA, Lam. The genus Platiris is divided into two sub-genera.
    Iridina, species which have crenulated margins; I. Ovata, I. exotica,
    Spatha, Lea; those with smooth or very slightly crenulated hinges, S.
    rubeus, S. Solenoides, Mycetopus, D'Orb. Fig. 151.

    PLATYLEPAS. ([Greek: platus], _platus_, wide; [Greek: lepas], _lepas_,
    rock.) _Order._ Sessile Cirripedes, Lam. _Fam._ Balanidea,
    Bl.--_Descr._ Conical, depressed, consisting of six valves, each
    divided internally by an angular plate jutting from the centre (like
    the buttress of a wall); operculum consisting of four valves in
    pairs.--_Obs._ This genus differs from Balanus, Coronula, &c. in the
    internal structure of the valves. De Blainville's description of
    Chthalamus partly agrees with this. Fig. 19.

    PLECTOPHORUS. Fer. ([Greek: plêktron], _plectron_, spur; [Greek:
    phoreô], _phoreo_, to carry.) A genus consisting of small testaceous
    appendages fixed on the posterior extremity of a species of slug. P.
    corninus, fig. 260.

    PLEIODON. Conrad. IRIDINA, Lam. _Fam._ Nayades, Lam.

    PLEKOCHEILUS. Guild. AURICULA Caprella, Lam. CARYCHIUM undulatum,
    Leach. (CAPRELLA, Nonnull.) This proposed genus is described as
    scarcely umbilical, dextral, oval, spiral; with the spire elevated,
    obtuse; the two last whorls very large, ventricose; aperture entire,
    elongated; columella with a single plait; the plait concave, inflected.
    Fig. 522, 523.

    PLEUROBRANCHUS. Cuv. ([Greek: Pleura], _pleura_, the side; _Branchiæ_,
    gills.) _Fam._ Semiphyllidiana, Lam. Subaplysiacea, Bl.--_Descr._
    Internal, thin, haliotoid, slightly convex towards the spiral apex;
    aperture entire.--_Obs._ This is a very light shell, delicately
    coloured, resembling Aplysia, but differing in the integrity of the
    margin. Fig. 232, P. membranaceus.

    PLEUROCERUS. Rafinesque. A genus very imperfectly described in the
    "Journal de Physique" as "oval, or pyramidal; aperture oblong; outer
    lip thin; inner lip truncated at the columella, which is smooth and
    tortuous, not umbilicated. Operculum horny or membranaceous." De
    Blainville, in giving this description, remarks that he has neither
    seen the animal nor the shell of this genus, which he imagines to have
    been formed from the "Paludine Coupée de M. Say."

    PLEURORYNCHUS. Phillips. ([Greek: Pleura], _pleura_, the side; [Greek:
    runchos], _rynchus_, a beak.) A genus founded upon a very singular
    species of CARDIUM, distinguished by the short anterior side, and the
    elongation of the hinge line into auricular processes, which are
    truncated at the extremities. C. Hibernicum from the Black Rock near
    Dublin, which is vulgarly called Asses-hoof, and C. elongatum (Sow.
    Min. Con. vol. I. 82.), form part of this genus.

    PLEUROTOMA. Lam. _Fam._ Canalifera, Lam. Siphonostomata, Bl.--_Descr._
    Fusiform, thick, in general ribbed or striated transversely; aperture
    oval, terminating anteriorly in an elongated canal; outer lip thin,
    with a fissure near its spiral extremity; columella smooth, nearly
    straight. Found principally in tropical climates.--_Obs._ This genus,
    which nearly resembles Fusus in other respects, may be known by the
    notch in the outer lip. The species differ in the length of the canal.
    Swainson has designated this genus a family, thus divided into genera:
    Brachytoma, in the description of which he says that the spire and
    aperture are of equal length, including the species strombiformis:
    Pleurotoma, in which the channel is so much lengthened, as to be little
    shorter than the spire: Clavatula, having the long narrow slit of
    Pleurotoma, but with a very short canal: Clavicantha, having the canal
    equally short, but the sinus or notch, instead of being linear and
    long, is short and wide; the surface is rough, and the whorls either
    coronated with prickles, or with compressed nodules resembling spines:
    Tomella, which has the spire and canal fusiform, but the spire of very
    few whorls, and the inner lip considerably thickened within where it
    joins the outer lip. Fig. 379, 389, P. marmorata; 381, P.
    Strombiformis, (Clavatula, Sw.)

    PLEUROTOMARIA. Defr. _Fam._ Turbinacea, Lam.--_Descr._ Turbinated,
    spiral; aperture sub-quadrate, with rounded angles; outer lip with a
    deep slit near its union with the spire.--_Obs._ This genus, which is
    only known in a fossil state, abounds in inferior Oolite, Oxford clay,
    and casts are found in a limestone bed in Norway. The Scissurellæ
    differ in being very minute shells, and are not so trochiform as the
    species of Pleurotomaria, P. reticulata, fig. 341.

    PLICACEA. Lam. A family of the order Trachelipoda, Lam. containing the
    following genera:

        1. PYRAMIDELLA. Pyramidal, with numerous whorls. Fig. 342.

        2. TORNATELLA. Cylindrical, with few whorls. Fig. 343, 344.

        3. RINGICULA. Margin reflected. Fig. 540, 541.

    PLICADOMUS. Sw. A sub-genus of Pupa, thus described: "spire moderate,
    regular and thick, but gradually conic; the tip obtuse; aperture
    perpendicular; inner lip wanting; outer lip semicircular; the margin
    dilated and reflected. P. sulcata, Chem. 135, f. 1231, 1232." Sw. p.
    332.

    PLICATED. (_Plicatus_, folded.) Applied to spiral plaits on the
    columella of some shells. _Ex._ Voluta, fig. 433. Also to the angular
    bendings in the margins of some bivalve shells. _Ex._ Dendostrea, fig.
    181.

    PLICATULA. Lam. (_Plicatus_, folded.) _Fam._ Pectenides, Lam.
    Sub-ostracea, Bl.--_Descr._ Irregular, sub-equivalve, sub-equilateral,
    attached by a small part of the surface of one valve, strongly
    plicated; umbones separated by a small, external ligamentary area;
    hinge with two cardinal teeth in each valve, two approximate in one
    valve, received between two distant in the other; cartilage placed
    between the cardinal teeth; muscular impressions one in each
    valve.--_Obs._ The cardinal teeth resembling those of Spondylus,
    distinguish this genus from others of the Lamarckian family Pectenides.
    Very few species are yet known, they are brought from the East and West
    Indies and the Philippine Islands. Fossil species are found in several
    of the supra-cretaceous beds. Fig. 178, P. gibbosa.

    PNEUMOBRANCHIA. Lam. The second section of the order Gasteropoda, Lam.
    containing the family Limacinea, fig. 256 to 263.

    PODOPSIS. Lam. This genus appears to have been described from specimens
    of a species of Spondylus, with the triangular disc broken out, so as
    to present a similarly shaped foramen, which was supposed to afford a
    passage for a large byssus.

    POLINICES. Montf. A genus composed of NATICA Mammilla, and other
    similar species, with mammillated spires, and the umbilicus filled with
    enamel. Fig. 327.

    POLLIA. Gray. TRITONIDEA, Sw. The name given by Gray was pre-occupied
    by a genus of Lepidopterous Insects.

    POLLICIPES. Leach. (_Pollex_, a thumb's breadth; _pes_, a foot.)
    _Order._ Pedunculated Cirripedes, Lam.--_Descr._ Conical, compressed,
    consisting of numerous valves, mostly in pairs, three or four pairs
    forming the principal part of the shell, and surrounded at the base by
    two or three rows of smaller valves, supported on a scaly, short
    pedicle.--_Obs._ This description will be found to exclude Scalpellum,
    and Smilium, the valves of which are more equal. The P. Mitellus, Auct.
    (fig. 37*), has been separated as a genus under the name of Mitellus by
    some authors, and it is certainly very different from P. polymerus,
    fig. 37, and P. cornucopia.

    POLLONTES. Montf. MILIOLA, Bl. A genus of microscopic Foraminifera.

    POLYBRANCHIATA. Bl. ([Greek: Polus], _polus_, many; _branchiæ_, gills.)
    The fifth family of the order Lamellibranchiata, Bl. containing the
    genera Arca, Pectunculus and Nucula, which have a series of small teeth
    on the hinge.

    POLYDONTES. Montf. ([Greek: Polus], _polus_, many; [Greek: odos],
    _odos_, tooth.) A species of Helix, shaped like CAROCOLLA, and having a
    number of teeth in the aperture.

    POLYGONAL. Many-sided.

    POLYGONUM. Schum. ([Greek: Polus], _polus_, many; [Greek: gônia],
    _gonia_, an angle.) A genus composed of species of TURBINELLA, Auct.
    which have large continuous costæ, so as to present the appearance of
    many-sided shells. T. polygonus, fig. 383. This generic name may be
    used to include all those species of Turbinella, Auct. which have very
    small folds on the columella.

    POLYGYRA. Say. A genus of Heliciform shells, characterized by the large
    number of close set whorls, constituting the spire. _Ex._ P.
    Septemvolvus, fig. 275, 276.

    POLYLEPAS. Bl. ([Greek: Polus], _polus_, many; [Greek: lepas], _lepas_,
    rock.) SCALPELLUM, Auct.

    POLYMORPHINA. D'Orb. A genus of microscopic Foraminifera.

    POLYPHEMUS. Montf. A genus composed of species of ACHATINA, Auct. which
    have elongated apertures, short spires, and an undulation in the outer
    lip. P. Glans, fig. 288.

    POLYPLAXIPHORA. Bl. The second class of the sub-type Malentozoa, Bl.
    containing the genus Chiton.

    POLYSTOMELLA. Lam. A genus of microscopic Foraminifera.

    POLYTHALAMACEA. Bl. ([Greek: Polus], _polus_, many; [Greek: THalamos],
    _thalamos_, chambers.) The third order of Cephalophora, Bl. the shells
    of which are described as straight, more or less symmetrically
    convolute, divided into several chambers. The septa are sometimes, but
    not always, pierced by one or more siphons. This order is divided into
    the families, Orthocerata, Lituacea, Cristacea, Ammonacea, Nautilacea,
    Turbinacea, Turriculacea, all of which contain genera of chambered
    shells. De Blainville arranges these families according to the degree
    in which the spires revolve. The first being straight, as the
    Orthocerata, and the last being so closely coiled up, that the last
    whorl covers the rest, as in the Nautilacea.

    POLYTHALAMIA. Lam. The first division of the order Cephalopoda, Lam.
    containing the following families of chambered shells, viz.
    Orthocerata, Lituacea, Cristacea, Sphærulacea, Radiolata, Nautilacea,
    Ammonacea. Fig. 463 to 484.

    POLYTROPA. Sw. A genus of "Scolyminæ," Sw. thus described:
    "Bucciniform; but the base narrow, and ending in a straight and
    contracted, but rather short, channel; spire longer, or as long as the
    aperture; exterior folliculated, or tuberculated; inner lip flattened,
    as in _Purpura_; basal notch small, oblique; no internal channel;
    crispata. En. Méth. 419, f. 2. Chem. 187, f. 1802. Capilla, Pennant,
    pl. 72, f. 89, imbricata. Mart. 122. f. 1124. ? rugosa. Chem. f.
    1473-4." Sw. p. 305.

    POLYXENES. Montf. A genus of microscopic Foraminifera.

    POMATIA. Gesner. (Gray, Syn. B. M. p. 133.) A genus of the family of
    "Cyclostomidæ," described as having "an elongated shell with reflexed
    lips, and a horny spiral operculum." Also a sub-genus of Snails,
    containing HELIX pomatia, Auct. (Gray's Turton, p. 135.)

    PORNUS. Humph. AMPULLARIA, Lam.

    PORCELLANA. Adanson. MARGINELLA, Auct.

    PORODRAGUS. Montf. A genus composed of species of Belemnites, placed by
    De Blainville in the section characterized as swelled near the apex,
    and straightened towards the base.

    POSIDONIA. Brong. A genus formed on the cast of a bivalve shell, common
    on schists from Dillemberg.

    POSTERIOR. (_After_, _behind_.) The posterior or hinder part of a
    bivalve shell, is that in which the siphonal tube of the animal is
    placed. It is known in the shell, by the direction of the curve in the
    umbones, which is from the posterior towards the anterior; also by the
    ligament, which is always placed on the posterior part of the hinge,
    when it exists only on one side of the umbones; and by the sinus (when
    there is one) in the palleal impression, which is always near the
    posterior muscular impression. In some shells, however, it is very
    difficult for a learner to trace these marks; such bivalves, for
    instance, as have the ligament spread out on both sides of the umbones;
    such as are nearly symmetrical, and have the umbones consequently
    straight, and a single muscular impression near the centre of the
    valve. The Brachiopodous bivalves have a different position, with
    relation to the animal, from the other bivalves, so that the hinge line
    is the posterior extremity, and the part where the valves open, is the
    anterior. The posterior extremity of the aperture of a spiral univalve
    shell, is that nearest to the spire. In patelliform shells the anterior
    and posterior extremities are distinguished by the muscular impression,
    which is annular, enclosing a central disc in the inner surface of the
    shell, excepting where it is interrupted by the place where the head of
    the animal lies, which of course is anterior. The posterior is marked
    _p._ in fig. 119, and 387. See ANTERIOR.

    POSTERO-BASAL MARGIN of a bivalve shell is the posterior side of the
    margin opposite the hinge.

    POSTERO-DORSAL MARGIN is the posterior side of the hinge.

    POTAMIS or POTAMIDES. Brong. A genus of fresh-water shells resembling
    Cerithium in the characters of the aperture, but which may be known
    from that genus by the thick, horny epidermis with which they are
    coated. P. muricata, fig. 377. (Cerithium, Sow.) We think that these
    shells should be placed near MELANIA.

    POTAMOMYA. A genus of shells resembling Corbula, in every respect
    except that of being inhabitants of fresh-water. Fig. 498, 499,
    represents one of these fresh-water Corbulæ.

    POTAMOPHILA. Sow. ([Greek: Potamis], _potamis_, river; [Greek:
    philios], _philios_, choice.) "Conques fluviatiles," Lam.--_Descr._
    Thick, equivalve, inequilateral, trigonal, covered with a greenish
    brown, smooth, horny epidermis; hinge thickened, broad, with one
    central, notched cardinal tooth in one valve, and two in the other,
    with indistinct lateral teeth; ligament large, supported on prominent
    fulcra; muscular impressions two in each valve, sub-orbicular.--_Obs._
    The name given to this shell refers to its place of abode, being found
    in rivers. It is the Venus sub-viridis of some authors, although being
    a fresh-water shell, and having an incrassated hinge, and a smooth,
    thick epidermis, it is most distinct from that genus. It is described
    by Bowdich under the name Megadesma, on account of its large ligament,
    and by Lamarck under that of Galathæa, a name previously used by him
    for a genus of Crustacea. P. radiata, fig. 115. Megadesma appears to be
    the preferable name, since it has the right of priority over
    Potamophila. It is found in Africa.

    PRIAMUS. A genus composed of ACHATINA Priamus, Lam. BUCCINUM
    Stercus--Pulicum, Chemn. Conch. 9. t. 120. f. 1026-7. This shell is
    ascertained to belong to a marine mollusc, having a horny operculum,
    and therefore is justly considered to form a distinct genus, allied to
    the Buccina and Struthiolariæ. Fig. 545.

    PRISODON. Schum. HYRIA, &c. Auct. Fig. 144.

    PRODUCED. (_Productus_, prominent.) A term applied to the spire of
    univalve shells, or to any other prominent portion.

    PRODUCTA. Sow. (_Productus_, produced.) _Fam._ Brachiopoda,
    Lam.--_Descr._ Equilateral, inequivalve, thick, striated; one valve
    generally convex, with the margin inflected, produced; the other valve
    flat, or slightly convex, with the margin reflected; hinge rectilinear,
    transverse.--_Obs._ The peculiarity of this genus, from which it
    derives its name, is the manner in which the anterior margins of the
    valves are drawn out and overwrap each other. The genus is only known
    in a fossil state. Species occur in Mountain Limestone, and Transition
    Limestone of older date. P. depressa, fig. 206.

    PROSERPINA. Gray? Fig. 274, represents a small shell belonging to the
    Helix tribe, to which it is believed, Mr. Gray has applied the name
    Proserpina nitida. We do not know how the genus is defined.

    PROTO. Defr. A fossil shell resembling TURRITELLA, but having a spiral
    band reaching to the centre of each valve. P. terebralis, Bl.

    PSAMMOBIA. Lam. _Fam._ Nymphacea, Lam.--_Descr._ Transverse, oblong,
    slightly gaping at both ends; hinge with two cardinal teeth in one
    valve, one in the other; ligament supported upon a prominent fulcrum;
    muscular impressions two in each valve, sub-orbicular, distant; palleal
    impression with a large sinus; epidermis thin.--_Obs._ The genus thus
    described includes PSAMMOTÆA of Lamarck, which, according to him, only
    differs in the number of teeth, and which he says are but "Psammobies
    dégenerées." The difference appears to be accidental. This genus
    differs from Tellina in not having a posterior fold in the margin. Fig.
    100. The species are found in temperate and tropical climates.

    PSAMMOCOLA. Bl. ([Greek: psammos], _psammos_, sand; _cola_, an
    inhabitant.) A name given by De Blainville to shells of the genus
    PSAMMOBIA, including PSAMMOTÆA of Lamarck.

    PSAMMOTÆA. See Lam. PSAMMOBIA.

    PSEUDOLIVA. Sw. A genus of "Eburninæ," Sw. thus described: "Shell
    thick, oval, oliviform, ventricose; spire very short, acute; base with
    two parallel grooves, one of which forms a notch at the base of the
    outer lip; suture slightly channelled; inner lip very thick, and
    turning inwards; aperture with an internal canal. Connects the
    TURBINELLIDÆ with the VOLUTIDÆ. P. plumbea, Chem. 188. f. 1806, 1807."
    Sw. p. 306.

    PSILOSTOMATA. Bl. The third family of Aporobranchiata, Bl. containing
    no genera of shells.

    PTEROCERAS. Auct. ([Greek: Pteron], _pteron_, a wing; [Greek: keras],
    _ceras_, horn.) _Fam._ Ailées, Lam.--_Descr._ Turrited, oval,
    ventricose, thick, tuberculated; spire short; aperture oval,
    terminating in a lengthened canal at both extremities; outer lip
    thickened, expanded, produced into horn-shaped, hollow, thickened
    spires, with an anterior sinus apart from the canal.--_Obs._ This
    genus, containing the shells commonly called Devil's Claws, Gouty
    Scorpions, Spiders, &c. is distinguished from Strombus by the
    digitations of the outer lip. No fossil species are known. Fig. 405, P.
    aurantiaca.

    PTEROCYCLOS. Benson. Syn. B. M. p. 133. A genus formed of species of
    Cyclostoma, Auct. which have "a groove or hole at the hinder part of
    the mouth."

    PTEROPODA. Lam. ([Greek: Pteron], _pteron_, a wing; [Greek: pous],
    _pous_, a foot.) The first order of the class Mollusca, Lam. consisting
    of molluscs whose organs of locomotion consist of a pair of wing-shaped
    fins. This order contains the genera Hyalæa, Clio, Cleodora,
    Spiratella, Cymbulia, and Pneumoderma. To which may be added other
    genera enumerated in explanation of figures 220 to 226. They may be
    thus distinguished.

        1. ATLANTA. Shaped like Nautilus, symmetrical. Fig. 220.

        2. SPIRATELLA. Spiral, not symmetrical. Fig. 224.

        3. CRESEIS. Straight, thorn-shaped. Fig. 222.

        4. VAGINULA. Straight, widened in the centre; apex pointed. Fig.
        225.

        5. CUVIERIA. The same; apex blunt. Fig. 223.

        6. CLEODORA. Aperture with three spines; apex recurved. Fig. 221.

        7. HYALÆA. Vaulted, open extremity, three-cornered; apex
        tridentate. Fig. 226.

    PTEROPODA. Bl. The second family of Nucleobranchiata, Bl. the shells of
    which are described as symmetrical, extremely thin, transparent,
    longitudinally enrolled, either forwards or backwards. The animals are
    remarkable for a pair of broad, flat, natatory organs or membranaceous
    fins, from which the family derives its name. It contains, in the
    system of De Blainville, the genera Atlanta, Spiratella, and Argonauta,
    to which may probably be added PHARETRIUM, König; ENTALIS, Defrance.

    PULLASTRA. Sow. _Fam._ Conques Marines, Lam.--_Descr._ Equivalve, ovate
    or oblong, transverse, inequilateral; hinge with three diverging
    cardinal teeth in each valve, notched at the terminations; muscular
    impressions two in each valve; palleal impression having a large sinus;
    ligament external, partly hidden by the dorsal margin.--_Obs._ This
    genus includes the Venerirupes of Lamarck, and several species of his
    Veneres, they are found in the sand on the shores of temperate and
    tropical climates. Fig. 120, P. textile.

    PULMONOBRANCHIATA. Bl. The first order of the first section of
    Paracephalophora monoica, containing the families Limnacea,
    Auriculacea, and Limacinea.

    PULVINITES. Defr. (_Pulvinus_, a cushion.) _Fam._ Malleacea,
    Lam.--_Descr._ Sub-equivalve, inequilateral, compressed, thin, slightly
    gaping posteriorly; one valve flat, the other rather concave; hinge
    linear, short, divided into perpendicular grooves; muscular impressions
    two, one sub-central, the other above it, nearer the hinge.--_Obs._
    This fossil shell is imperfectly known, and it is difficult to give a
    sufficient reason for separating it from Perna. It comes from the
    Baculite limestone of Normandy. Fig. 170, P. Adansonii.

    PUNCTATED. (_Punctatus_, spotted or dotted.) For example, see Conus
    Nussatella. Fig. 460.

    PUNCTICULIS. Sw. A sub-genus of "Coronaxis," Sw. (Conus) described in
    Swainson's Malacology, page 311.

    PUNCTURELLA. Lowe. CEMORIA, Leach.

    PUPA. Auct. _Fam._ Colimacea, Lam.; Limacinea, Bl.--_Descr._
    Cylindrical, generally ribbed; spire long, obtuse, composed of numerous
    slowly increasing whorls; aperture sub-quadrate, rounded anteriorly,
    entire; outer lip thickened; columella plaited.--_Obs._ This genus is
    composed of land shells very variable in form, differing from Bulinus
    in the numerous slowly increasing whorls of the spire, and in the plicæ
    on the columella, and from Clausilia in the want of a clausium.
    Britain, Southern Europe, East and West Indies, Mexico, &c. P. Uva.
    Fig. 291.

    PUPELLA. Sw. A sub-genus of Clausilia. Lardn. Cyclop. Malac. p. 334.

    PUPILLA. Leach. A sub-genus of Pupa, P. marginata, Auct. (Gray's
    Turton, p. 196.)

    PUPINA. Vignard. MOULINSIA, Grateloup. _Fam._ Colimacea, Lam.--_Descr._
    Pupiform, sub-cylindrical; last whorl less than the preceding; surface
    brilliantly polished; suture of the spire enamelled; aperture circular;
    peritreme thickened; a notch at the base of the inner lip; operculum
    horny, spiral.--_Obs._ The species upon which this genus was originally
    founded, and described in the "Annal des Sciences Naturelles," tome 18,
    p. 439, (December 1829,) is a small pupiform shell, having nothing to
    distinguish it but the enamelled suture and the notch in the aperture;
    characters quite insufficient in themselves for the purpose of generic
    distinction; at the same time sufficient to lead M. De Ferussac to the
    suspicion of its having an operculum. The next species, described by
    Grateloup under the name of Moulinsia Nunezii, (Ann. Soc. Linn. Burd,
    Nov. 1840), presents more remarkable characters, having the spire
    turned backwards and the penultimate whorl disproportionately large.
    Seven additional species have been lately brought to this country from
    the Philippine Islands by Mr. Cuming. They will be described by the
    author in the Zoological Proceedings for 1841, and an illustrated
    monograph of the whole genus is published in the Thesaurus
    Conchyliorum, Part I, by the Author. It may be observed that in one of
    the new species, the notch in the peritreme almost disappears, leaving
    a very slight sinus. Fig. 524, 526, 527, 528.

    PURPURA. Auct. ("_The shell-fish from which purple is taken_," Plin.)
    _Fam._ Purpurifera, Lam. Entomostomata, Bl.--_Descr._ Oval or oblong,
    thick; spire for the most part short, sometimes rather longer; external
    surface generally sulcated, granulated, tuberculated or muricated;
    aperture long, oval, somewhat dilated, emarginated anteriorly; outer
    lip crenated, acute; columella flattened; operculum horny, with the
    nucleus lateral, thin towards the columella.--_Obs._ True Purpuræ to be
    found in the Lamarckian genera Buccinum, Ricinula, and others. They may
    be generally distinguished by the flatness of the columellar lip, and
    by the short canal or emargination, which is not reflected or raised,
    as in Buccinum. The species are very numerous and very variable in
    form, inhabiting the seas of temperate and tropical climates. The
    animals secrete a purple liquor, which has been used advantageously for
    dyeing; the origin of the famous Tyrian dye. Fig. 414, P. persica.

    PURPURIFERA. Lam. (_Purpura_, purple; _fero_, to carry.) A family
    belonging to the second section of Lamarck's order Trachelipoda, the
    shells of which are described as having a very short recurved, or
    ascending canal, or else only a notch between the inner and outer lips.
    The name Purpurifera has been given to the family because the animals
    which it includes, and particularly the genus Purpura, contain the
    colouring matter from which the ancients obtained the well known
    splendid purple. This family contains the following genera.

        1. CASSIS. Outer lip thick, reflected, denticulated, canal turned
        suddenly over the back; spire short; including _Cassidea_ and
        _Cypræcassis_. Fig. 410 to 412.

        2. CASSIDARIA. Canal turned gently upwards. Fig. 407, 408.

        3. ONISCIA. Inner lip granulated; canal short. Fig. 409.

        4. BUCCINUM. Outer lip thickened not reflected; canal short;
        including _Cyllene_ and _Phos._ Fig. 416, 421, 422, 425.

        5. NASSA. The same, with a notch or tooth at the extremity of the
        columella; including _Cyclops_. Fig. 423, 424.

        6. DOLIUM. Swelled, grooved spirally; outer lip not reflected. Fig.
        420.

        7. PURPURA. Aperture large; columellar lip flat; including
        Tritonidea. Fig. 414, 415.

        8. MONOCEROS. The same, with a tooth on the outer lip. Fig. 417.

        9. CONCHOLEPAS. Patelliform; aperture as large as the shell. Fig.
        417.

        10. RICINULA. Columellar and outer lips granulated, denticulated,
        outer lip digitated; including _Tribulus_. Fig. 413.

        11. TRICHOTROPIS. Hairs on the epidermis, along the keels. Fig.
        429.

        12. TEREBRA. Elongated, with a spiral groove near the suture of the
        whorls. Fig. 428.

        13. BULLIA. Short; aperture wide; outer lip marginated. Fig. 427.

        14. EBURNA. Like Buccinum, but the outer lip not thickened. Fig.
        426.

        15. HARPA. With varices at regular intervals. Fig. 419.

    PUSIA. Sw. A sub-genus of Tiara (Mitra.) (Sw. Malac. p. 320.)

    PUSIODON. Sw. A genus of "Lucerninæ," Sw. (Helix) thus described:
    "Shell flattened, smooth; the body-whorl large, and much dilated at the
    aperture; spire small, flat, of three or four contracted whorls;
    aperture very oblique, sinuated, or obsoletely toothed at the base of
    the outer lip, which is spreading and sub-reflected; inner lip
    obsolete; umbilicus open. Zonaria Chemn. 132. f. 1188. auriculata Zool.
    Ill. I. pl. 6." Sw. Malac. p. 330.

    PUSIOSTOMA. Sw. A genus of the family "Columbellinæ." Sw. Thus
    described: "general form of Columbella, but the outer lip is only
    toothed in the middle, where it is greatly thickened; inner lip convex
    between the granular teeth; punctata, E. M. 374. f. 4. mendicaria, 375.
    f. 10. turturina, 314. f. 2. fulgurans. Lam." Sw. Malac. p. 313.

    PUSTULARIA. Sw. A genus of "Cypræinæ," Sw. thus described: "Shell
    generally marked by elevated pustules; aperture narrow and linear; the
    extremities more or less produced; the teeth continued beyond, and
    frequently forming elevated striæ across the lips. P. Cicercula, P.
    Globulus." Sw. Malac. p. 324.

    PYGMÆA. Humph. COLUMBELLA, Auct.

    PYLORIDEA. Bl. The ninth family of the order Lamellibranchiata, Bl. the
    shells of which are described as nearly always regular, rarely
    otherwise, nearly always equivalve, gaping at both extremities; hinge
    incomplete, the teeth becoming gradually obsolete; two distinct
    muscular impressions; palleal impression very flexuous posteriorly.
    This family is divided into: Section 1. Ligament internal; Pandora,
    Thracia, Anatina, Mya, Lutricola. Section 2. Ligament external;
    Psammocola, Soletellina, Solen, Sanguinolaria, Solenocurtus, Solenimya,
    Panopæa, Glycimeris, Saxicava, Byssomya, Rhomboides, Hiatella,
    Gastrochæna, Clavagella, Aspergillum.

    PYRAMIDAL. (_Pyramidalis._) Resembling a pyramid in form. _Ex._
    Cerithium Telescopium, fig. 378.

    PYRAMIDELLA. Lam. (_A little pyramid._) _Fam._ Plicacea, Lam.
    AURICULACEA, Bl.--_Descr._ Pyramidal, smooth, polished; spire long,
    pointed, composed of numerous whorls; aperture small, modified by the
    last whorl, rounded anteriorly; outer lip slightly expanded; columella
    tortuous, with several folds. This is a genus of small, polished,
    marine shells. Pyramidella Terebellum, fig. 342.

    PYRAZUS. Montf. POTAMIS, Brongniart.

    PYRELLA. Sw. A genus consisting of Turbinella Spirilla, Auct. and
    similar species, having a long channel, a pyriform outline, and one
    strong plait at the base of the columella, the apex of the spire is
    enlarged. P. Spirillus, fig. 384. (The proper term would be Spirilla.)

    PYRIFORM. (_Pyrum_, a pear; _forma_, shape.) Shaped like a pear, i. e.
    large and rounding at one end, and gradually tapering at the other.
    _Ex._ Pyrula, fig. 390.

    PYRGO. Defr. A genus of microscopic Foraminifera.

    PYRGOMA. Auct. ([Greek: Purgos], _pyrgus_, a tower.) _Order_, Sessile
    Cirripedes, Lam.--_Descr._ Composed of a single conical, hollow paries,
    with a small aperture closed by an operculum of four valves, and
    supported upon a cup-shaped base.--_Obs._ The genera into which Leach
    has divided this genus are Pyrgoma, Adna, and Megatrema; his genera
    Nobia and Savignium differ in having but two valves for the operculum.
    Pyrgoma differs from Creusia in having the body of the shell, i. e. the
    parietal cone, simple, not divided into valves. Fig. 31.

    PYRGOPOLON. De Montfort's figure of this genus appears as if it had
    been drawn from the nucleus of a Belemnite.

    PYRULA. Auct. (_A little pear._) _Fam._ Canalifera, Lam.
    Siphonostomata, Bl.--_Descr._ Thin, oblong, pyriform, ventricose
    towards the spire, gradually tapering towards the anterior of the
    aperture, spire short, consisting of few volutions; aperture wide,
    terminating in a long, narrow, open, canal; columella smooth, elegantly
    tortuous.--_Obs._ The above description includes all the true Fig
    shells, which present a most graceful form; the contour partaking of
    the peculiar curve, called by painters the line of beauty. P. Ficus,
    fig. 390.

    PYRUM. Humph. PYRULA, Lam.

    QUADRATE. (_Quadratus._) Square, applied when the outline of shells is
    formed by nearly straight lines meeting at right angles.

    QUADRILATERAL. Four-sided.

    QUINQUELOCULINA. D'Orbigny. A genus of microscopic Foraminifera.

    RADIATING. (_Radians._) A term applied to the ribs, striæ, bands of
    colours, &c. when they meet in a point at the umbones of a bivalve
    shell, and spread out towards the ventral margin.--_Ex._ The bands of
    colour in Tellina radiata, fig. 105.

    RADICATED. (_Radix_, a root.) Attached, and as it were rooted by means
    of a fibrous byssus.

    RADIOLATA. Lam. A family belonging to the order Cephalopoda, Lam. The
    shells belonging to it are described as discoidal, with the spire
    central, and the chambers radiating from the centre to the
    circumference. This family contains the genera Rotalina, Lenticulina,
    and Placentula.

    RADIOLITES. A genus belonging to the family of Rudistes, differing from
    Sphærulites, in having both the valves more conical.

    RADIUS. Montf. A genus composed of OVULUM Volva, Auct. and other
    similar species, having a long attenuated canal at each extremity. Fig.
    442.

    RADIX. Montf. A genus composed of species of LIMNÆA, having a short
    spire and wide aperture.--_Ex._ L. aperta, fig. 309.

    RAMIFIED. (_Ramus_, a branch.) Branched out.--_Ex._ The varices of some
    Murices, &c.

    RAMPHIDOMA. Schum. POLLICIPES, Leach.

    RAMOSE. (_Ramosus_, branched.) Spread out into branches. _Ex._ Murex
    inflatus, fig. 395.

    RANELLA. Auct. (_Rana_, a frog.) _Fam_. Canalifera, _Lam._
    Siphonostomata, Bl.--_Descr._ Oval or oblong, depressed, thick, with
    two rows of continuous varices, skirting the outline, one on each side;
    spire rather short, pyramidal, acute, aperture oval, terminating in a
    canal at each extremity; outer lip thickened within, crenulated, or
    denticulated, forming an external varix; inner lip spread over a
    portion of the body whorl.--_Obs._ The shells composing this
    well-defined genus, are for the most part covered with tuberculations,
    and granulations, and from the colour and squat shape of some species,
    have been likened to frogs. The Ranellæ are mostly inhabitants of the
    East Indian seas. The few fossil species known, occur in the tertiary
    beds. The two continuous rows of varices skirting the spire,
    distinguish this genus from Triton, which it nearly approaches, and
    into which some species run by imperceptible gradations. Fig. 393, 394.
    Many new species were brought to this country by Mr. Cuming, and are
    represented in parts 84, 85, 88, 89, 92, 93, of the author's
    Conchological Illustrations.

    RANGIA. Desmoulins. GNATHODON, Gray.

    RAPANUS. Schum.? A genus consisting of species of PYRULA, Auct. which
    are thin, much inflated, with short canals. Fig. 389, P. papyracea.

    RAPELLA. Sw. A genus of "Pyrulinæ," Sw. thus described: "Shell
    ventricose, generally thin, almost globose; the base suddenly
    contracted, and forming a short canal, the channel almost obsolete;
    umbilicus large, partly concealed by the inner lip. R. papyracea. En.
    Méth. 436, f. 1." Sw. p. 307. RAPANUS, Schum. Fig. 389.

    RAPHANISTER. Montf. A species of madrepore, described as a shell.

    RAPUM. Humph. TURBINELLA, Lam.

    RAZOR SHELL. A common name by which shells of the genus Solen, are
    known in the market.

    RECTILINEAR. (_Rectus_, right; _linea_, a line.) In a straight line.
    _Ex._ The hinge of Byssoarca Noæ, fig. 132.

    RECURVED. (_Re_, back; _curvo_, to bend.) Turned backwards; the term,
    when applied to symmetrical conical univalves, is used to signify that
    the apex is turned towards the posterior margin, as in Emarginula, fig.
    241.

    REFLECTED. (_Reflected_, to fold back.) Turned, or folded backwards.
    _Ex._ The edge of the outer lip in Bulinus, fig. 282, is _reflected_,
    while that of Cypræa, fig. 445 to 450, is _inflected_.

    REMOTE. (_Remotus_, distant.) Remote lateral teeth in a bivalve shell,
    are those that are placed at a distance from the cardinal teeth. _Ex._
    The lateral teeth of Aphrodita, (fig. 123.) are remote; those of Donax,
    (fig. 108) are near.

    RENIELLA. Sw. A sub-genus of Malleus. Lardn. Cyclop. Malac. p. 886.
    Gray states it to be only a distorted specimen of Vulsella, Syn. B. M.
    p. 145.

    RENIFORM. (_Ren_, a kidney; _forma_, shape.) Shaped like a kidney.
    _Ex._ The aperture of Ampullaria, fig. 318.

    RENULINA. Lam. A genus of microscopic Foraminifera.

    REOPHAX. Montf. A genus of microscopic Orthocerata, Bl.

    REPENT. (_Repens_, creeping.) A term applied to those shells, which,
    being attached by the whole length of their shell, give the idea of
    creeping or crawling. _Ex._ Vermilia, fig. 7.

    RETICULATED. (_Reticulatus._) Resembling net-work.

    RETIFERA. Bl. The first family of the order Cervicobranchiata, Bl.
    containing the genus Patella.

    REVERSED or SINISTRAL SHELLS, are those in which the aperture is on the
    left side of the shell, while it is held with the mouth downwards, and
    towards the observer. _Ex._ Balea, fig. 296. Attached bivalves are said
    to be reversed, when the left valve is free, instead of the right; a
    circumstance which sometimes occurs in Chama and Ostrea.

    RHEDA. Humph. HYALÆA, Lam.

    RHINOCLAVIS. Sw. A genus of "Cerithinæ," Sw. thus described: "channel
    curved backwards, in an erect position; inner lip very thick, with a
    tumid margin; pillar generally with a central plait; operculum
    ear-shaped; lineatum. En. M. 443, fig. 3, Vertagus. Ib. f. 2,
    subulatum. Lam. No. 23, fasciatum. Mart. 157, f. 1481. obeliscus, En.
    Méth. 443, f. 4; aluco, Ib. f. 5, (Aberrant,) semi-granosum. Ib. 443,
    f. 1, asperum. Mart. 157, f. 1483."

    RHINOCURUS. Montf. A genus of microscopic Foraminifera.

    RHINODOMUS. Sw. A genus of "Scolyminæ," Sw. thus described: No internal
    groove; shell clavate; the spire longer than, or equal with the
    aperture; the whorls with ridges or longitudinal varices, and rendered
    hispid by transverse grooves; inner lip wanting; pillar with a terminal
    fold; aperture striated; outer lip with a basal sinus. R. senticosus,
    Chem. tab. 193. f. 1864-1866.

    RHIZORUS. Montf. A genus described from a microscopic shell, appearing
    to be a cylindrical Bulla.

    RHODOSTOMA. Sw. A sub-genus of "Turbininæ," Sw. p. 344.

    RHOMBOIDAL. ([Greek: rhomboeidos], _rhomboeidus_.) Having a rhombic
    form, i. e. four-sided; two sides meeting at acute, two at obtuse,
    angles. Conchologists are not very strict in the application of this
    term, for, indeed, a perfect rhomboidal figure could not be found among
    all the testaceous productions of the sea.

    RHOMBOIDES. Bl. A genus described as resembling Byssomya in the shell,
    but differing in the animal. MYTILUS rugosus, Gmelin. HYPOGÆA barbata,
    Poli.

    RHOMBUS. Montf. ([Greek: rhombos], _rhombos_, a rhomb.) A genus
    consisting of species of CONUS, having a rhomboidal or quadrilateral
    form and a coronated spire. _Ex._ Conus nocturnus, fig. 459.

    RICINULA. Lam. (Resembling the seed-vessel of the _Ricinus_.) _Fam._
    Purpurifera, Lam. Entomostomata, Bl.--_Descr._ Sub-ovate, thick,
    tuberculated; spire short; aperture narrow, terminating anteriorly in a
    short canal; outer-lip thickened, denticulated within, digitated
    without; columellar lip spread over a portion of the body whorl, and
    granulated.--_Obs._ This interesting genus is composed of some neat
    little shells allied to Purpura, from which they are distinguished by
    the finger-like branching of the outer lip, and the granulations of the
    columella. Fig. 413, R. Horrida.

    RIGHT. See DEXTRAL.

    RIMULA. Defr. A genus consisting of a minute species of EMARGINULA,
    Auct. which has a fissure near the margin, but not reaching it. R.
    Blainvillii, fig. 243.

    RIMULINA. D'Orbigny. A genus of microscopic Foraminifera.

    RINGICULA. Deshayes. A genus founded on Auricula ringens of Lamarck and
    several small fossils, resembling in some respects Pedipes of Adanson;
    they would belong to Tornatella, were it not for the lips being
    thickened and marginated, fig. 540, A. ringens.

    RISSOA. Freminville. _Fam._ Ellipsostomata, Bl. Melaniana,
    Lam.--_Descr._ Oblong, turrited, acuminated; spire long, consisting of
    numerous whorls; aperture round or oval, pointed posteriorly, dilated
    anteriorly; outer lip slightly thickened, emarginated, operculum
    horny.--_Obs._ The Rissoæ are small white, marine shells, considered by
    some authors as resembling Melaniæ, but placed by Sowerby near the
    Scalariæ. They are principally from the shores of the Mediterranean,
    and are also very abundant on the British shores, as well as the East
    and West Indian. Fig. 346, R. reticulata.

    ROBULUS. Montf. A genus of microscopic Foraminifera.

    ROLLUS. Montf. A genus composed of CONUS Geographus, Auct. fig. 462,
    and other species, rather cylindrical in form, and having a coronated
    spire.

    ROSALINA. D'Orb. A genus of microscopic Foraminifera.

    ROSTELLARIA. (From _rostrum_, a beak.) _Fam._ Alatæ, Lam.
    Siphonostomata, Bl.--_Descr._ Turrited, fusiform, thick, smooth or
    ribbed; aperture oval, terminating anteriorly in a long canal,
    posteriorly in a channel running up the spire; outer lip dilated,
    thickened, sometimes digitated, running up all or part of the spire,
    with a sinus near the anterior canal; inner lip smooth, spread over
    part of the body whorl and of the spire. The Red Sea and the Indian
    Ocean produce the few known species of this genus.--_Obs._ HIPPOCHRENES
    is the name given by De Montfort, to those fossil species which have
    the outer lip simple and very much dilated. R. curvirostrum, fig. 412.
    APORRHAIS is a name given to another proposed genus, composed of
    Rostellaria pes-pelecani, Auct. fig. 404. and similar species.

    ROSTRATED. (From _rostrum_, a beak.) Having one or more protruding
    points, as Tellina rostrata.

    ROTALIA. Lam. A genus of microscopic Foraminifera. The same as
    Rotalites of De Montfort.

    ROTELLA. Lam. (_A little wheel._) _Fam._ Turbinacea, Lam.--_Descr._
    Orbicular, generally smooth, shining; spire conical, depressed, short;
    aperture subtrigonal; outer lip thin, angulated near the centre; inner
    lip spread over the surface of the whorls, forming a thickened disc.
    Operculum horny, orbicular, spiral, with numerous whorls.--_Obs._ The
    pretty little shells thus described are found in seas of tropical
    climates. They are distinguished from other genera of the family by
    their lenticular form and the orbicular callosity of the under surface.
    Fig. 357, R. vestiaria.

    RUDISTES. Lam. A family of the order Conchifera Monomyaria, Lam. the
    shells of which are described as irregular, very inequivalve, without
    distinct umbones; the ligament, hinge and animal entirely unknown. The
    shells contained in this family may be thus distinguished.

        1. CALCEOLA. Large valve conical; attached by a flat space between
        the umbones, which form the extremities of the shell. Fig. 194.

        2. HIPPURITES. Large valve cylindrical, with two internal lobes or
        varices. Fig. 198.

        3. SPHÆRULITES. Large valve attached, including _Radiolites_.
        Birostrites is proved to be the cast of a Sphærulites. Fig. 193,
        196.

        4. HIPPONYX. Flat valve attached, upper valve conical. Fig. 199,
        200.

    RUDISTES. Bl. The second order of the class Acephalophora, Bl.
    containing the genera Sphærulites, Crania, Hippurites, Radiolites,
    Birostrites and Calceola.

    RUDOLPHUS. Lam. MONOCEROS, Auct.

    RUFOUS. Reddish brown.

    RUGOSE. Rough, rugged.

    RUPELLARIA. Fl. de Belvue. An unfigured shell placed by De Blainville
    in a division of the genus Venerirupis.

    RUPICOLA. Fl. de Belvue. A shell described by De Blainville as an
    equivalve, terebrating species of ANATINA. A. rupicola, Lam.

    SABINEA. A genus of shells resembling small species of LITTORINA, as L.
    Ulvæ, &c. of our shores.

    SADDLE OYSTER. PLACUNA Sella, so called on account of a resemblance in
    shape to a saddle; the part near the umbones being flat, and the
    ventral margins being turned up in a sort of fluting or peak.

    SAGITTA. (_An arrow._) An ancient name for Belemnites.

    SALIENT. (_Saliens._) Jutting out, prominent.

    SALPACEA. Bl. The second family of the order Heterobranchiata, Bl.
    containing no genera of shells.

    SANDALINA. Schum. CREPIDULINA, Lam. A genus of microscopic
    Foraminifera.

    SANGUINOLARIA. Lam. (_Sanguis_, blood.) _Fam._ Nymphacea, Lam.
    Pyloridea, Bl.--_Descr._ Equivalve, inequilateral, transverse,
    sub-ovate, rounded anteriorly, sub-rostrate posteriorly, compressed,
    thin, covered with a shining epidermis, gaping at the sides; hinge with
    two cardinal teeth in each valve, and an external ligament supported
    upon a prominent fulcrum; muscular impressions two in each valve,
    lateral, irregular, palleal impressions with a large sinus.--_Obs._
    This description is made to exclude some of Lamarck's species of
    Sanguinolaria, such as S. occidens, S. rugosa, which are Psammobiæ; and
    to include others which he has left out. The Sanguinolariæ are
    sub-rostrated posteriorly, while the Psammobiæ are sub-quadrate and
    have a posterior angle. Fig. 98, S. rosea. Sandy shores of tropical
    climates.

    SARACENARIA. Defr. A genus of microscopic Foraminifera.

    SAVIGNIUM. Leach. A genus of Sessile Cirripedes, described as composed
    of four valves soldered together, and a convex bivalve operculum; the
    ventral and posterior valve on each side being soldered together, in
    other respects resembling PYRGOMA. Fig. 30.

    SAXICAVA. Fl. de Belvue. Journ. de Ph. an. 10. (_Saxum_, a stone;
    _cava_, a hollow.) _Fam._ Lithophagidæ, Lam. Pyloridea, Bl.--_Descr._
    Transverse, irregular, generally oblong, inequilateral, sub-equivalve,
    gaping anteriorly; ligament external; muscular impressions two,
    lateral; palleal impression interrupted, not sinuated; hinge, when
    young with sometimes two or three minute, obtuse, generally indistinct,
    cardinal teeth; which become obsolete when full grown.--_Obs._ Several
    genera have been founded only upon the difference between the young and
    old shell of the same species of this genus. The Saxicavæ are found in
    the little hollows of rocks; in cavities on the backs of oysters, of
    roots of sea-weeds, &c. in northern and temperate climates. S. rugosa,
    fig. 94.

    SCABRICULA. Sw. A sub-genus of Mitræ, consisting of species which have
    a roughened external surface, &c. Sw. Malac. p. 319.

    SCABROUS. Rough.

    SCALA. Klein. SCALARIA, Auct.

    SCALARIA. Auct. _Fam._ Scalariana, Lam. Cricostomata, Bl.--_Descr._
    Turrited, oval or oblong; spire long, composed of rounded, sometimes
    separate whorls, surrounded by regular concentric ribs; aperture oval,
    peristome reflected continuous, entire.--_Obs._ The typical species of
    this genus, commonly called the Wentletrap, (S. pretiosa) is celebrated
    for the beautiful appearance caused by the numerous ribs encircling the
    whorls, and formerly produced an immense price in the market. It is
    brought from China. There are many smaller species, some of which are
    equally elegant. Fig. 351, S. Pallasii, Kiener.

    SCALARIANA. Lam. A family belonging to the first section of the order
    Trachelipoda, Lam. The shells belonging to it are described as having
    the inner and outer lips continuous, without a canal, emargination, or
    other division. In this respect the family is stated to differ from the
    Turbinacea, and is therefore separated. The genera may be distinguished
    as follows:--

        1. VERMETUS. Irregularly twisted, like Serpula. Fig. 345.

        2. EULIMA. Pyramidal; apex contorted; including _Bonellia_. Fig.
        347, 348.

        3. RISSOA. Pyramidal, straight, consisting of few whorls. Fig. 346.

        4. SCALARIA. With external varices. Fig. 351.

        5. CIRRUS. Trochiform. Fig. 349.

        6. ENOMPHALUS. Orbicular. Fig. 350.

        7. DELPHINULA. Few whorls, rapidly increasing. Fig. 352.

    SCALLOP. The common name for shells of the genus Pecten, the larger
    species of which were worn by pilgrims to the Holy Land in the time of
    the Crusades.

    SCALPELLUM. Leach. (A little knife or lancet.) _Order_, Pedunculated
    Cirripedes, Lam.--_Descr._ Flat, quadrated, acuminated, composed of
    thirteen valves, one dorsal, arcuated; one pair apicial, acuminated;
    one pair ventral; two pair lateral, small, sub-quadrate; pedicle
    scaly.--_Obs._ This genus and _Smilium_, are the only Pedunculated
    Cirripedes which have thirteen valves; in the latter genus, which we
    think should at any rate be united to this, the valves are somewhat
    differently placed, and the pedicle is said to be smooth. Fig. 35,
    Scalpellum vulgare. British.

    SCAPHA. Klein. (_A boat._) NAVICELLA, Auct.

    SCAPHANDER. Montf. BULLA lignaria, Auct. Fig. 251.

    SCAPHELLA. Sw. A genus of the family "Volutinæ," Sw. thus described:
    "Shell smooth, almost polished; outer lip thickened internally; suture
    enamelled; lower plaits the smallest; apex of the spire various: 1.
    fusiformis. Sw. Bligh. Cat. 2. undulatus. _Ex._ Conch. pl. 27. 3.
    Junonia, _Ex._ Conch. pl. 33. 4. stromboides. 5. papillosa. Sw. Sow.
    gen." Sw. Malac. p. 318.

    SCAPHITES. (_A boat._) _Fam._ Ammonacea, Lam. and Bl.--_Descr._
    Convolute, chambered, closely related to the Ammonites, from which it
    differs in the last whorl being eccentrically straightened, and
    lengthened, and again incurved towards the extremity. Only known in a
    fossil state. Fig. 481, S. æqualis.

    SCAPHULA. Sw. A genus of "OLIVINÆ," Sw. thus described: "Spire very
    short, thick, obtuse, and not defined; aperture very wide, with only
    two or three oblique plaits at the base. Sw. patula, _Sow._ Tank. Cat.
    2331. (_b._)" (Sw. p. 322.)

    SCARABUS. Montf. (_Scarabæus_, a kind of beetle.) _Fam._ Colimacea,
    Lam. Auriculacea, Fer.--_Descr._ Oval, somewhat compressed, smooth,
    with slightly raised varices; spire equal in length to the aperture,
    pointed, consisting of numerous whorls; aperture ovate, rounded
    anteriorly, pointed posteriorly, modified by the last whorl; outer lip
    sub-reflected, with several prominent folds on the inner edge; inner
    lip spread over a portion of the body whorls, with several prominent
    folds.--_Obs._ The shells of this genus are found like Auriculæ, in
    marshy places. C. imbrium is said to have been found on the tops of
    mountains, by Captain Freycinet. Fig. 299*, S. imbrium.

    SCHIZODESMA. Gray. A genus composed of species of MACTRA, Auct. with
    the ligament placed in an external slit. Fig. 8, M. Spengleri.

    SCISSURELLA. D'Orbigny. (_Scissus_, cut.) _Fam._ Turbinacea,
    Lam.--_Descr._ Sub-globose, umbilicated, with a spiral groove
    terminating at the margin of the outer lip in a slit; spire short;
    aperture oval, modified by the last whorl; outer lip sharp, with a deep
    slit near the spire. Recent on the coasts of Britain; fossil in the
    Calcaire-grossièr.--_Obs._ This genus, consisting of small shells, is
    known from Pleurotomaria by the shortness of the spire; the latter
    genus being trochiform. Fig. 340, S. elatior.

    SCOLYMUS. Sw. A genus of the family "Scolyminæ." Sw. (Turbinella) thus
    described: "Sub-fusiform, armed with foliated spines; spire shorter;
    pillar with distinct plaits in the middle." The species enumerated are,
    "cornigerus, pugillaris, Globulus, Rhinoceros, ceramicus, Capitellum,
    umbilicaris, mitis." Sw. Malac. p. 304.

    SCORTIMUS. Montf. A genus of microscopic Foraminifera.

    SCROBICULARIA. Schum. Species of LUTRARIA, Act. of a rounded shape.
    LIGULA, Leach.

    SCROBICULATED. (_Scrobiculus_, a little ditch or furrow.) Having small
    ditches or furrows marked on the surface.

    SCUTELLA. Brod. (_Scutellum_, a little shield.) _Fam._ Phyllidiana,
    Lam.--_Descr._ Shaped like Ancylus, pearly within; apex posteriorly
    inclined, central, involute; muscular impressions two, oblong, ovate,
    lateral; aperture large, ovate.--_Obs._ This genus is intermediate
    between Ancylus and Patella; while in the aspect of the beak, the
    observer is reminded of Navicella.

    SCUTIBRANCHIATA. Bl. (_Scutum_, a shield; _branchiæ_, gills.) The third
    order of Paracephalophora Hermaphrodita, Bl. containing animals with
    patelliform, but not symmetrical shells, and divided into the families
    Otidea and Calyptracea.

    SCUTUM. Montf. (_A shield._) PARMOPHORUS ELONGATUS, Lam.

    SECURIFORM. (_Securis_, an axe; _forma_, shape.) Hatchet-shaped. _Ex._
    Pedum, fig. 179.

    SEDENTARY ANNELIDES. Lam. The third order of the class Annelides, Lam.
    distinguished from the two other orders by the circumstance of the
    animal being enveloped by a shelly tube which it never entirely leaves.
    The order is divided into the families Dorsalia, Maldania, Serpulacea,
    and Amphitrites. Fig. 1 to 13.

    SEA DATE. The common name for PHOLAS Dactylus in the market, given to
    it on account of its cylindrical shape. Fig. 35.

    SEGMENTINA. Flem. NAUTILUS Lacustris, Montagu. Test. Brit. Planorbis
    nitidus, Drap. tab. 2. Fig. 17 to 19.

    SEMICORDATE. Half heart-shaped.

    SEMIDISCOIDAL. Forming the half of a circular disc.

    SEMILUNAR. Half moon-shaped.

    SENECTUS. Humph. A genus of "Senectinæ," thus described by Swainson:
    "Imperforate; the base produced into a broad flat lobe, spire rather
    elevated and pointed; the whorls convex; aperture perfectly round; not
    more oblique than _Helix_; inner lip entirely wanting, imperialis.
    Mart. 180. f. 1790. marmoratus. l. M. 448. f. 1." Sw. p. 348.

    SEMIPHYLLIDIANA. Lam. The second family of the order Gasteropoda, Lam.
    the genera of which are distinguished as follows:--

        1. UMBRELLA, round, flat; apex central, muscular impression not
        interrupted. Fig. 233.

        2. PLEUROBRANCHUS, apex lateral, sub-spiral. Fig. 232.

    SENOCLITA. Schum. CINERAS, Leach.

    SEPTARIA. Lam. See TEREDO.

    SEPTUM. (Lat.) An enclosure, applied to the thin plate of Crepidula,
    fig. 239; also to the plates dividing the chambers of multilocular
    shells.

    SERAPHS. Montf. TEREBELLUM convolutum, Lam. Fig. 451.

    SERPULA. Auct. (_A little serpent._) _Fam._ Surpulacea, Lam.--_Descr._
    Tubular, narrow, pointed at the apex, gradually widening towards the
    aperture, attached irregularly, sometimes spirally, twisted,
    imbricated; keeled or plain; aperture generally round, with the edge
    simple, or angulated by the termination of external ribs or
    keels.--_Obs._ This description is intended to include the genera
    Serpula, Spirorbis, Vermilia, Galeolaria, &c. The Serpulæ abound in all
    seas, on rocky shores, at any time covered by water, attached to any
    kind of marine substance, whether moveable or stationary. The fossil
    species occur in almost all tertiary strata. Fig. 4 to 7.

    SERPULACEA. Lam. The fourth family of the order Sedentary Annelides,
    Lam. containing the following genera of tubular, irregular shells.

        1. SERPULA, attached by a small portion of the shell. Fig. 4.

        2. SPIRORBIS, attached by the whole length, coiled. Fig. 5.

        3. Galeolaria, with the open extremity raised, and the aperture
        tongue-shaped. Fig. 6.

        4. VERMILIA, attached by the whole length, straight or waved. Fig.
        7.

        5. SPIROGLYPHUS, which hollows a bed in the body to which it is
        attached. Fig. 8.

           Sowerby. (Genera of Shells, published at 50, Great Russell
        Street, Bloomsbury,) gives satisfactory reasons for re-uniting the
        whole of the preceding under the name SERPULA.

        6. MAGILUS, which burrows in coral; outer lip reflected. Fig. 9 to
        10.

        7. LEPTOCONCHUS, outer lip reflected. Fig. 11.

        8. STYLIFER, spiral, thin, globular, living in Starfish. Fig. 12,
        13.

           The three last genera should certainly find some other place in
        the system.

    SESSILE CIRRIPEDES. Lam. (_Sessilis_, low, dwarfish.) An order of
    Cirripedes, consisting of those which are attached by the base of the
    shells, containing the genera Tubicinella, Balanus, Coronula, Acasta,
    Pyrgoma, Creusia. To which may be added some other genera enumerated in
    explanation of figures 14 to 33. The shells of the Sessile Cirripedes
    consist of two different sets of valves: 1st. The _parietal_ valves, or
    pieces arranged in a circle, side by side, around the body of the
    animal, (an arrangement designated _coronular_ by De Blainville.) 2nd.
    The _opercular_ valves, or pieces placed so as to enclose the aperture.
    Between those opercular valves the ciliæ protrude which characterize
    the class. Besides these two sets of valves, there is generally a
    shelly plate, serving as a sort of foundation to the rest. The Sessile
    Cirripedes may be thus arranged.

        1. TUBICINELLA. Six parietal valves, tube-shaped, opercular valves
        perpendicular. Fig. 14.

        2. CORONULA. Six parietal valves, opercular valves horizontal. Fig.
        15, 16, 17, 18.

           These two genera fix themselves in the skin of the Whale. The
        latter has been divided into the genera Chelonobia, Cetopirus,
        Diadema, and Chthalamus.

        3. PLATYLEPAS. Valves divided, each having a prominent internal
        plate. Fig. 19.

        4. CLITIA. Parietal valves four, opercular valves two, valves
        dove-tailed into each other. Fig. 20.

        5. ELMINEUS. Parietal valves four, opercular valves four. Fig. 22.

        6. CONIA. Parietal valves four, thick and porous at the base. Fig.
        21.

        7. OCTOMERIS. Parietal valves eight. Fig. 24.

        8. CATOPHRAGMUS. Parietal valves numerous, irregular. Fig. 23.

        9. BALANUS. Parietal valves six; opercular valves four, placed
        against each other conically in pairs. This genus has been divided
        into Acasta, Conoplea, Chirona, and Balanus. Fig. 25, 26, 27.

        10. CREUSIA. Parietal valves four, supported on the edge of a
        funnel-shaped cavity. Fig. 28.

        11. PYRGOMA. Paries simple, supported on a cavity. This genus has
        been divided into the genera Nobia, Savignium, Pyrgoma, Adna,
        Megatrema, and Daracia. Fig. 29 to 33.

    SETIFEROUS. Hairy.

    SHANK SHELL. The vulgar name for the shell designated Murex Rapa. It is
    used in Ceylon for ornamental purposes.

    SIDEROLITES. Montf. A genus of microscopic Foraminifera.

    SIGARETUS. Lam. _Fam._ Macrostomata, Lam.--_Descr._ Suborbicular,
    oblique, haliotoid, thick; spire depressed, consisting of two or three
    rapidly increasing whorls; aperture wide, entire, modified by the last
    whorl, the width exceeding the length; columella tortuous; inner lip
    spread thinly over part of the body whorl; epidermis thin.--_Obs._ This
    genus is distinguished from Natica, by the width of the aperture, and
    the absence of the umbilical callosity. It may be known from Stomatia,
    and Stomatella, by the texture, which in Sigaretus, is never pearly as
    in Stomatia, the former being partly an internal shell. Fig. 334, S.
    concavus. Mostly brought from tropical climates.

    SILIQUA. Megerle. (A husk, or pod.) LEGUMINARIA, Schum. A genus
    composed of species of SOLEN, Auct. which have an internal rib. Fig.
    51, Solen radiatus.

    SILIQUARIA. Brug. _Fam._ Cricostomata, Bl. Dorsalia, Lam.--_Descr._
    Tubular, rugose, spiral near the apex, irregularly twisted near the
    aperture, with a longitudinal fissure radiating from the apex, and
    proceeding through all the whorls and sinuosities of the tube.--_Obs._
    This genus was included in Serpula by Linnæus, from which, however, it
    is distinguished by the longitudinal slit, fig. 1. S. anguina. The
    recent species are found in the sponges with siliceous spiculæ, in the
    Mediterranean; the fossils in tertiary beds.

    SIMPLE. (_Simplex_, lat.) Single, entire, uninterrupted, undivided.

    SIMPLEGAS. Mont. 1, 83. (_Simplex_, simple; [Greek: gastêr], _gaster_,
    belly.) A genus described by De Blainville, as being discoidal, and
    having the spire uncovered like AMMONITES, but having the chambers
    divided, by simple septa, like Nautilus.--_Obs._ The septa of the shell
    named Simplegas by De Montfort, are evidently sinuous, according to his
    figure. Fig. 475, S. sulcata.

    SINISTRAL. (_Sinister_, left.) On the left side. A sinistral shell is a
    _reversed_ one. The sinistral valve of a bivalve shell may be known, by
    placing the shell, with its ligamentary or posterior part towards the
    observer; the sides of the shell will then correspond with his right
    and left side.

    SINUOUS. Winding, serpentine. The septa of Ammonites are sinuous. The
    muscular impression of the mantle, or palleal impression of some
    bivalve shells, is sinuated near the posterior muscular impression.

    SINUS. (_Sinus_, a winding, or bay.) A winding or tortuous excavation.
    The sinus in the outer lip of Strombus, fig. 406; and that in the
    muscular impression of Venus, will be indicated by the letter _s_.

    SIPHON. ([Greek: Siphon], siphon.) A pipe, or tube. A shelly tube
    passing through the septa of chambered shells. It is said to be
    _dorsal_, _central_, or _ventral_, according to its situation near the
    outer, or inner parts of the whorl. See Introduction.

    SIPHONAL SCAR. The name applied by Mr. Gray, to the opening or winding
    sinus in the palleal impression of a bivalve shell, in the place where
    the siphonal tube of the animal passes.

    SIPHONARIA. Sow. ([Greek: Siphon], siphon.) _Fam._ Phyllidiana, Lam.
    Patelloidea, Bl.--_Descr._ Patelliform, depressed, inclining to oval,
    ribbed; apex nearly central, obliquely inclining towards the posterior
    margin; muscular impression partly encircling the central disc, but
    interrupted in front, where the head of the animal reposes, and at the
    side by a siphon, or canal passing from the apex to the margin.--_Obs._
    This siphon, which is in some species very distinct, serves to
    distinguish this genus from Patella. S. Sipho, fig. 231*.

    SIPHONOBRANCHIATA. Bl. (_Siphon_, and _Branchiæ_, gills.) The first
    order of Paracephalophora Dioica, Bl. divided into the families
    Siphonostomata, Entomostomata, and Angiostomata.

    SIPHONOSTOMA. Guild. A sub-genus of Pupa, consisting of several
    elongated species, which have the aperture detached from the whorls;
    such as P. costata, and fasciata.

    SIPHONOSTOMATA. Bl. ([Greek: Siphon], _siphon_; [Greek: stoma],
    _stoma_, mouth.) The first family of Siphonobranchiata, Bl. the shells
    of which are extremely variable in form, but always have a canal or
    notch at the anterior extremity of the aperture. This family partly
    answers to the Canalifera of Lamarck and the genus Murex in the system
    of Linnæus. It contains the genera Pleurotoma, Rostellaria, Fusus,
    Pyrula, Fasciolaria, Turbinella, Columbella, Triton, Murex, Ranella,
    and Struthiolaria.

    SIPHUNCLE. (Siphunculus.) A small siphon.

    SISTRUM. Montf. RICINULA, Auct. fig. 413.

    SKENEA. _Flem._ A genus including some species of EUOMPHALUS and
    CIRRUS.

    SMILUM. Leach. _Fam._ Pedunculated Cirripedes.--_Descr._ Thirteen
    pieces, ten of which are in pairs, lateral, subtriangular; one
    posterior dorsal, linear; all smooth; peduncle hairy.--_Obs._ This
    genus is distinguished from Pentelasmis, by the number of its valves,
    and from Scalpellum, by the hairy peduncle. S. Peronii, fig. 36.

    SNAIL. The common garden Snail, so destructive to our vegetables,
    belongs to the genus Helix. The water snail, found in ponds, is
    Planorbis.

    SOL. Humph. A genus consisting of several species of the genus Trochus,
    and corresponding with the sub-genus Tubicanthus, Sw. Malac. Fig. 349.

    SOLARIUM. Auct. (_A terrace, or gallery_.) _Fam._ Turbinacea, Lam.
    Goniostomata, Bl.--_Descr._ Discoidal beneath, conical above, with a
    wide umbilicus, the spiral margin of which is angulated and crenulated;
    aperture trapezoidal; peritreme thin, sharp; columella straight;
    operculum horny, subspiral.--_Obs._ The Solarium Perspectivum, is
    commonly called the Staircase Trochus, from the angulated edges of the
    whorls being seen through the umbilicus, which reaches to the apex, and
    presents the appearance of a winding gallery. The species are not
    numerous, they belong to tropical climates. A few fossil species occur
    in the tertiary formations. Fig. 353, S. Perspectivum.

    SOLDANIA. D'Orb. A genus of microscopic Foraminifera.

    SOLEN. Auct. (_A kind of shell-fish_, Plin.) _Fam._ Solenacea, Lam.
    Pyloridea, Bl.--_Descr._ Bivalve, transversely elongated,
    sub-cylindrical, equivalve, very inequilateral, gaping at both
    extremities, umbones terminal, close to the anterior extremity; hinge
    linear, with several small cardinal teeth, and a long, external
    ligament; muscular impressions distant, anterior tongue-shaped, placed
    behind the cardinal teeth, posterior irregular, sub-ovate; palleal
    impression long, bilobed posteriorly.--_Obs._ The above description of
    the genus Solen, is framed so as to admit only those species which are
    commonly called Razor Shells, with the umbones terminal, and the
    anterior muscular impression behind them. They are found buried deep in
    the sand, in a perpendicular position, their situation being pointed
    out by a dimple, on the surface. They are abundant in temperate
    climates. Some of the Lamarckian Solenes will be found in the genus
    Solenocurtus, Bl. Fig. 60, 61.

    SOLENACEA. Lam. A family of the order Conchifera, Dimyaria Lam. The
    shells belonging to it are described as transversely elongated,
    destitute of accessary pieces, gaping only at the lateral extremities;
    ligament external.--The genera may be thus distinguished.

        1. SOLEN. Razor shells, truncated at the extremities. Fig. 60.

        2. PANOPÆA. Broad, with prominent tooth. Fig. 65, 66.

        3. SOLENOCURTUS. Rounded at the extremities, with internal bar.
        Fig. 61.

        4. SOLENIMYA. No teeth, epidermis over-reaching the shell. Fig. 68.

        5. GLYCIMERIS. Thick, fulcrum of the ligament prominent. Fig. 67.

        6. LEPTON. Flat, scale-shaped. Fig 62.

        7. NOVACULINA. Umbones nearly central; covered by a thin epidermis.
        Fig. 63.

        8. GLAUCONOME. Oval, margins close. Fig. 64.

    SOLENELLA. Sow. (_Solen._) _Fam._ Arcacea, Lam.--_Descr._ Oval,
    equivalve, subequilateral, compressed, covered with a thin, shining,
    olive-green epidermis; hinge with three or four anterior, and numerous
    sharp posterior lateral teeth, arranged in a straight line; muscular
    impressions two, lateral; palleal impression with a large sinus;
    ligament external, prominent, elongated.--_Obs._ This genus partakes of
    the characters of the genus Nucula, and of the family Solenacea. A few
    specimens of the only species known (S. Norrisii, fig. 138.) were
    dredged by Mr. Cuming at Valparaiso.

    SOLENIMYA. Lam. (Solen and Mya.) _Fam._ Mactracea, Lau. Pyloridea,
    Bl.--_Descr._ Equivalve, inequilateral, transversely oblong, rounded at
    the extremities with the umbones near the posterior side, covered with
    a shining brown epidermis extending beyond the edges of the shell;
    hinge without teeth; ligament partly internal, placed in the margin of
    an oblique, flattish, posterior rib; muscular impressions two, distant,
    lateral. From the Mediterranean, Australian, and Atlantic
    Oceans.--_Obs._ Solenimya differs from Solenocurtus and the true
    Solens, in having the posterior side of the shell the shortest; in the
    internal ligament; and in being destitute of teeth. It resembles
    Glycimeris, but is not incrassated. Fig. 68, Solenimya radiata.

    SOLENOCURTUS. Bl. (_Solen_ and _curtus_, short.) _Fam._ Pyloridea, Bl.
    Solenacea, Lam.--_Descr._ Oval, elongated, equivalve, sub-equilateral,
    with the edges nearly straight and parallel, and the extremities rather
    truncated; umbones not very prominent, sub-central; hinge with or
    without two or three rudimentary cardinal teeth; ligament prominent,
    placed upon thick callosities; muscular impressions two, distant,
    rounded; palleal impression straight, with a deep sinus. East
    Indies--_Obs._ Distinguished from the true Solenes by the central
    position of the umbones and an internal bar reaching partly across the
    shell.

    SOLETELLINA. Bl. SANGUINOLARIA radiata. S. Diphos, f. 99. S. livida of
    Sowerby, and similar species, are placed together in this genus.

    SPATHA. Lea. A sub-genus of IRIDINÆ, consisting of I. rubens and I.
    nilotica, which have not distinctly crenulated margins. Spatha
    solenoides, of Lea, is the genus Mycetopus D'Orbigny. Fig. 151.

    SPHÆNIA. Turt. A genus consisting of a small species resembling
    Saxicava, in general appearance, but having a spoon-shaped process on
    the hinge of one valve. S. Binghamii, Fig. 96.

    SPHÆROIDINA. D'Orb. A genus of microscopic Foraminifera.

    SPHÆRULACEA. Bl. The first family of Cellulacea consisting of the
    following genera of microscopic Foraminifera: Miliola, Melonia,
    Saracenaria, Textularia.

    SPHÆRULACEA. Lam. The fourth family of Cephalopoda, Lam. described as
    multilocular, globular, sphærical, or oval, with the whorls enveloping
    each other; some of them have a particular internal cavity, and are
    composed of a series of elongated, straight and contiguous chambers
    which altogether form a covering for the internal cavity. This family
    contains the genera Miliola, Gyrogona and Melonia.

    SPHÆRULITES. Lam. (_Sphæra_, a sphere.) _Fam._ Rudistes, Lam. and
    Bl.--_Descr._ Orbicular, inequivalve, irregularly foliated outside;
    lower valve cup-shaped, depressed; upper valve nearly flat, like an
    operculum.--_Obs._ These fossils are not regarded as shells by all
    conchologists. S. foliacea, Fig. 193.

    SPHINCTERULUS. Montf. LENTICULINA, Bl. A genus of microscopic
    Foraminifera.

    SPINES. (_Spina_, a thorn.) Thin, pointed spikes.

    SPINOSE. (Spinosus.) Having spines or elevated points, as Neritina
    spinosa. Fig. 325.

    SPIRAL. (_Spira_, a spire.) Revolving outwards from a central apex or
    nucleus, like the spring of a watch. A shell or an operculum, may be
    spiral, without being produced into a pyramid. Bands of colour, striæ,
    grooves, &c. commencing from the nucleus and following the volutions of
    the shell, are described by the above word.

    SPIRAMILLA. Bl. A genus of Serpulacea, differing from other Serpulæ
    principally in the characters of the animal.

    SPIRATELLA. Bl. LIMACINEA, Lam. Fig. 224.

    SPIRE. (_Spira._) The cone or pyramid produced in a non-symmetrical
    univalve by its oblique revolution downwards from the apex or nucleus.
    The spire, in descriptions, includes all the volutions above the
    aperture. See Introduction.

    SPIRIFER. Sow. (_Spira_, a spire; _fero_, to bear.) _Order_,
    Brachiopoda, Lam.--_Descr._ Transverse, equilateral; hinge linear,
    straight, widely extended on both sides of the umbones, which are
    separated by a flat area in the upper and larger valve; this area is
    divided in the centre by a triangular pit for the passage of the
    byssus; interior with two spirally convolute appendages.--_Obs._ This
    genus, which is only known in a fossil state, is distinguished from
    Terebratula externally, by the flat area in one valve, internally, by
    the singular spiral process from which the above name is derived. Fig.
    214, 215. Most of the species belong to the mountain or carboniferous
    limestone.

    SPIROGLYPHUS. Daud. A genus consisting of a species of Serpula _Auct._
    which makes a groove for itself in the surface of shells. Serpula
    spirorbis, var. Dillwyn. Fig. 8.

    SPIROLINA. Lam. A genus of microscopic Foraminifera.

    SPIROLOCULINA. D'Orb. A genus of microscopic Foraminifera.

    SPIRORBIS. Lam. A genus composed of species of SERPULA, Auct. which are
    coiled round in a spiral disc like a snake at rest. S. nautiloides,
    fig. 5, is the common little white shell, found upon the shell of
    lobsters.

    SPIRULA. (_Spira_, a winding compass.) _Fam._ Lituolata, Lam. Lituacea,
    Bl.--_Descr._ Convolute, smooth, symmetrical, discoid, with parallel
    unconnected whorls, divided into numerous chambers by transverse septa;
    siphon continuous.--_Obs._ This pretty little shell is partly internal,
    only a part of it being visible when on the animal. Fig. 471.

    SPISULA. Gray. A genus composed of MACTRA fragilis, and other similar
    species, which have the ligament sub-external, marginal, not separate
    from the cartilage; with the posterior lateral teeth double in one
    valve, and single in the other. M. fragilis, fig. 80, is the species
    figured for Spisula in Mr. Gray's paper on the Mactradæ, in the second
    series of Loudon's Magazine of Natural History. We have since learned,
    however, that it was figured there by mistake, not having been intended
    for a Spisula, but belonging more properly to the genus Mactra, as
    defined by Mr. Gray, whose description of Spisula, is as
    follows:--"Shell ovate, trigonal, sub-angular at each end. Hinge and
    lateral teeth as in Mactra, but hinge of left tooth small. Siphonal
    inflexion ovate." The principal difference between Spisula and Mactra
    is, that the ligament is not separated from the cartilage in the
    former.

    SPONDYLUS. Auct. (_A shell-fish_, Ancients.) _Fam._ Pectenides, Lam.
    Sub-ostracea, Bl.--_Descr._ Inequivalve, sub-equilateral, irregularly
    foliaceous and spinose, auriculated, denticulated at the margins,
    attached by the lower and deeper valve; hinge rectilinear, with two
    prominent teeth in each valve, locking into corresponding cavities in
    the opposite valve; umbones separated by a broad, elongated, triangular
    disc in the lower valve; ligament contained in a groove, dividing the
    triangular area in the centre; muscular impressions one in each valve,
    sub-central, sub-orbicular. The Mediterranean, East and West Indies,
    and China, produce Spondyli most abundantly.--_Obs._ This genus is
    remarkable for the richness and beauty of the spines and foliations,
    which adorn the external surface of most of the species, the splendid
    colours by which many of them are varied, and the natural groupings
    formed by their attachment to each other. Fig. 177, and Frontispiece.

    SPORULUS. Montf. A genus of microscopic Foraminifera.

    SQUAMOSE. (_Squama_, a scale.) Scaly, covered with scales, as the
    pedicle of Pollicipes Mitellus, fig. 37*.

    STENOPUS. Guild. ([Greek: Stenos], narrow, [Greek: pous], foot.) A
    genus nearly "allied to the Linnæan Helices, from all of which it
    differs in the curious contraction of the pedal disc, and the caudal
    tentaculum furnished with a gland beneath." The shell is described as
    heliciform, umbilicated, transparent, with the aperture transverse. The
    two species described are Stenopus cruentatus and lividus; they are
    both from the Caribbæan Islands, Guild. Zool. Journ. xii. p. 528, tab.
    15, f. 1 to 5.

    STOMATELLA. Lam. See STOMATIA.

    STOMATIA. Auct. ([Greek: stoma], _stoma_, mouth.) _Fam._ Macrostomata,
    Lam.--_Descr._ Sub-orbicular, oblong, auriform, variegated without,
    iridescent within; spire depressed; aperture entire, very wide,
    oblique; peritreme uninterrupted. _Obs._ This genus is known from
    Haliotis by being destitute of the series of holes; is distinguished
    from Sigaretus by the substance of the shell, the latter being
    internal, and never pearly. Our description includes STOMATELLA, Lam.
    The Stomatiæ are marine, and belong to the East Indies and New Holland.
    Fig. 335, S. Phymotis.

    STORILLUS. Montf. 1, 131. A genus of microscopic Foraminifera, included
    in the genus Rotalites in M. De Blainville's system.

    STRAPAROLLUS. Mont. A genus containing some species of HELIX, Auct.
    Generic characters not defined.

    STREPTAXIS. Gray. _Fam._ Colimacea, Lam.--_Descr._ Ovate, or oblong;
    when young, sub-hemispherical, deeply umbilicated, with rapidly
    enlarging whorls. At length the penultimate whorl is bent towards the
    right and dorsal side of the axis, and the umbilicus becomes depressed,
    and often nearly closed. The mouth is lunulate, the edge slightly
    thickened and reflected, and often with a single tooth on the outer
    side of the inner lip.--_Obs._ This genus of land shells is separated
    from Helix on account of the eccentricity of the penultimate whorl. S.
    contusa, fig. 269.

    STRIATED. (_Stria_, a groove.) Marked with fine grooves or lines.

    STRIGOCEPHALUS. Defr. PENTAMERUS, Sow.? GYPIDIA, Dalman.

    STROMBUS. Auct. _Fam._ Alatæ, Lam. Angiostomata, Bl.--_Descr._ Oblong,
    turrited, rather ventricose, solid; aperture generally lengthened,
    terminating posteriorly in a short canal, and anteriorly in an
    emargination or truncated canal; outer lip, when young, thin; when full
    grown, thickened and expanded, lobed at the spiral extremity, sinuated
    anteriorly near the caudal canal.--_Obs._ This well known genus
    includes some species of immense size, commonly called conch shells.
    Most of the recent species are brought from the Indian Ocean. Very few
    fossil species are known. The young shells have very much the
    appearance of cones, the outer lips being thin. There are also several
    species which do not, even when full grown, thicken their outer lips
    very considerably. The genus Strombus is distinguished from
    Rostellaria, by the notch in the outer lip, which in the latter genus
    is close to the canal. Fig. 406, S. pugilis.

    STROPHOMENA. Rafinesque. ORTHIS, Dalman.

    STROPHOSTOMA. Deshayes. A fossil shell, of the family of Colimacea,
    Lam. in some degree resembling Anostoma, having the aperture turned
    upwards towards the spire, it is, however, umbilicated, and is said to
    have an operculum resembling that of Cyclostoma. It is the Ferussina of
    Grateloup. Fig. 534, 5, 6.

    STRUTHIOLARIA. Auct. (_Struthio_, an Ostrich.) _Fam._ Canalifera,
    Lam.--_Descr._ Oblong, turrited, thick; spire turrited, composed of
    several angulated whorls; aperture oval, sub-quadrate, oblique; outer
    lip thickened, reflected, advancing in the centre, receding towards the
    extremities; inner lip thickened, expanded over the columella and part
    of the body whorl.--_Obs._ This singular genus, consisting of three or
    four recent species, is named "Pied D'Autruche" by the French, on
    account of some resemblance in the outer lip to the foot of the
    Ostrich. From New Zealand. Fig. 391, S. straminea.

    STYLIFER. Brod. (_Stylus_, a style; _fero_, to bear.)--_Descr._ Thin,
    pellucid, turbinated; apex a little out of the perpendicular; aperture
    wide anteriorly, gradually narrowing towards the spiral extremity,
    where it terminates acutely.--_Obs._ This is a genus of small,
    transparent shells, found burrowing in the rays of Starfish. There are
    but two or three species at present known, one of which is elongated
    like Terebra, the other nearly globular. Fig. 12, S. astericola. West
    Indies, Gallapagos, and Britain.

    STYLINA. Flem. STYLIFER, Brod.

    SUB. (_under._) Used as a prefix and signifying nearly. Thus a
    bivalve-shell, the valves of which are nearly alike, would be described
    as _sub_-equivalve.

    SUB-APLYSIACEA. Bl. The first family of the order Monopleurobranchiata,
    Bl. containing several genera of Mollusca without shells, and the genus
    Pleurobranchus.

    SUB-BIVALVES. A term of distinction applied by De Blainville, to those
    spiral univalves which have an operculum; these, as they constitute two
    distinct pieces, he considers as forming a medium between univalves and
    bivalves.

    SUB-MYTILACEA. Bl. The sixth family of the order Lamellibranchiata, Bl.
    the shells belonging to which are described as free, rather pearly,
    regular, equivalve; hinge dorsal, laminated; ligament external; two
    muscular impressions; palleal impression not sinuated. This family,
    with the exception of the last genus, agrees with the family Nayades of
    Lamarck, and contains the genera Anodon, Unio, and Cardita.

    SUB-OSTRACEA. Bl. The second family of Lamellibranchiata, Bl. the
    shells of which are described as of a compact texture, sub-symmetrical;
    with the hinge rather complex; one single, sub-central, muscular
    impression, without any traces of palleal impression. This family
    corresponds with the Pectenides of Lamarck, and part of the genus
    Ostrea in the system of Linnæus. It contains the genera Spondylus,
    Plicatula, Hinnites, Pecten, Pedum, Lima.

    SUB-SPIRAL. Not sufficiently spiral to form a complete volution.

    SUBULA. Bl. (_An awl._) A generic name under which M. De Blainville
    includes TEREBRA maculata, Auct. f. 428, together with nearly all the
    species of Terebra, enumerated by Lamarck and other authors; only
    leaving in the latter genus those species, which being more bulbous, or
    ventricose, nearly resemble Buccinum in general form. These last
    mentioned species, such as Terebra buccinoidea, (fig. 247) have been
    formed into a new genus by Mr. Gray, under the name Bullia. If both
    these genera were adopted, the genus Terebra would be extinct.

    SUBULATE. (_Subula_, an awl.) A term applied to shells which are long
    and pointed as in Terebra. Fig. 427, 428.

    SUCCINEA. Drap. (_Succinum_, amber.) _Fam._ Colimacea, Lam. Limacinea,
    Bl. _Sub-genus_, Cochlohydra, Fer.--_Descr._ Ovate, rather elongated;
    aperture large, entire, longitudinal; spire short; outer lip thin,
    continuous with the thin, sharp-edged columella; inner lip spread over
    a part of the body-whorl.--_Obs._ The shells belonging to this genus of
    partly amphibious mollusca, are distinguished from Limnæa by not having
    a fold on the columella The S. amphibia is of a bright amber colour.
    Fig. 265, 266. Temperate and tropical climates.

    SULCATED. (SULCATUS, lat.) Having grooves or furrows.

    SULCI. Grooves or furrows.

    SUTURE. (_Sutura_, lat.) A seam, stitch, joining together. Applied
    particularly to the line which marks the joining of the whorls of the
    spire. The suture is distinguished as _simple_, as in most cases; or
    _double_, when accompanied by a parallel groove close to it;
    _marginated_, when produced into a ledge by the matter which fills up
    and covers it; _obsolete_, when it is filled up so as not to be
    visible, as in the case of Ancillaria.

    SYLVICOLA. Humph. CYCLOSTOMA, Lam.

    SYMMETRICAL, ([Greek: sun], _syn_, similar; [Greek: metron], _metron_,
    proportion.) Both sides alike. Although the term is used thus as one of
    distinction, it is to be observed that no shells are strictly and
    perfectly symmetrical; even in the Nautilus, the apex verges in a
    slight degree towards one side of the shell. Two kinds of univalve are
    symmetrical, or nearly so; 1st. Those which are symmetrically
    convolute, as the Nautilacea and the Ammonacea, which are spiral; 2nd.
    Those which are not spiral, but simply conical, as the patelliform
    shells. Bivalves belonging to the Brachiopoda are also symmetrical.
    _Ex._ Patella, fig. 229. Ammonites, fig. 478.

    SYMPHYNOTA. Lea. A genus of Nayades, in which Mr. Lea proposed to
    include species of the genus UNIO, the valves of which are connate, or
    united at the dorsal margin. We believe that this distinction, as a
    genus, has been abandoned by its author. The fact is, that all the
    Uniones are Symphynotæ when in a young state. In Unio Alatus, (fig.
    147) and Dipsas plicatus, (fig. 142) it will be observed that the
    valves have not separated at the dorsal edge, but are broken lower
    down.

    TAPADA. (Gray. Turton. p. 127.) A division of the genus HELIX,
    containing HELIX aperta, Auct. or the Tapada snail.

    TAPES. Schum. PULLASTRA. Sow.?

    TECTUS. Montf. A genus composed of species of the genus Trochus, having
    elevated, conical spires, and columella notched or truncated by a
    spiral fold. Fig. 359. Trochus maculatus, presents an example.

    TELEBOIS. Montf. A genus of microscopic Foraminifera.

    TELESCOPIUM. Montf. CERITHIUM Telescopium, Auct. fig. 378.

    TELLINA. Linn. _Fam._ Nymphacea, Lam. Conchacea, Bl.--_Descr._
    Sub-equivalve, inequilateral, compressed, rounded anteriorly, slightly
    beaked or angulated posteriorly, the posterior ventral margin having a
    flexuosity; hinge with two cardinal and generally two lateral teeth in
    each valve; muscular impressions, two in each valve, remote; palleal
    impression with a large sinus.--_Obs._ The fold or bending in the
    posterior margin distinguishes this genus from others which it nearly
    resembles. It is composed of some bivalves of great beauty and variety,
    which are found in nearly all climates. Fig. 105, T. radiata, 106, T.
    lingua-felis.

    TELLINIDES. Lam. _Fam._ Nymphacea, Lam.--_Descr._ Sub-equivalve,
    inequilateral, transverse, compressed, rounded anteriorly, slightly
    beaked or angulated posteriorly; hinge with two cardinal teeth in each
    valve, and one lateral tooth in one valve, very near the cardinal
    teeth. Muscular impressions two, distant, palleal impression with a
    large sinus. _Obs._ This genus is distinguished from Tellina in having
    but one lateral tooth near the cardinal teeth. Fig. 107, T. rosea.
    Tropical.

    TENUIPEDES. (_Tenuis_, slender; _pedes_, feet.) The second section of
    the order Conchifera Dimyaria, divided into the families Mactracea,
    Corbulacea, Lithophagidæ, Nymphacea.

    TERACLITA. Schum. CONIA, Auct.

    TEREBELLUM. Lam. (_Terebra_, an augur?) _Fam._ Convolutæ, Lam.
    Angyostomata, Bl.--_Descr._ Smooth, slender, oblong, sub-cylindrical;
    spire obtuse, short, sometimes hidden; (Seraphs, Montf.) aperture long,
    narrow posteriorly, wider anteriorly; outer lip slightly thickened,
    truncated, unconnected at the base with the columella; inner lip thin,
    smooth, nearly straight, spread over a portion of the body-whorl,
    continued in a ridge above the sutures of the spire.--_Obs._ Montfort
    has separated the fossil species with hidden spires, under the name
    Seraphs. (T. convolutum, Lam.) Only one recent species is known, of
    which there are several varieties, one spotted, one marked in
    sub-spiral lines, another in patches. It is brought from the East
    Indies. Fig. 451, T. convolutum; 452, T. subulatum.

    TEREBRA. (_An augur, a piercer._) _Fam._ Purpurifera, Lam.
    Entomostomata, Bl.--_Descr._ Subulate, elongated, pointed, turrited;
    spire long, consisting of numerous whorls; aperture small terminating
    in a short, reflected canal; outer lip thin; columella tortuous;
    operculum horny. The recent species are mostly tropical.--_Obs._ Nearly
    all the species enumerated by Lamarck and other authors are included by
    De Blainville in his genus Subula; those few species which that
    conchologist left in the present genus, being shorter and more
    ventricose than the others, approximate in shape to some of the
    Buccina, and are distinguished by Mr. Gray under the generic name
    Bullia. It seems strange, that De Blainville, being convinced of the
    necessity of separating the two groups, and consequently applying a new
    generic term to one of them, should have given that term to the larger
    number and the more typical species of the Lamarckian genus. Fig. 427,
    Bullia vittata. (Terebra.) Fig. 428, Terebra maculata. (Subula.)

    TEREBRALIA. Sw. A genus of "Cerithinæ," Sw. thus described: "Outer lip
    much dilated, generally uniting at its base to the inner lip; leaving a
    round perforation at the base of the pillar; channel truncate;
    operculum round: palustre. Mart. f. 1472." Sw. p. 315.

    TEREBRATING SHELLS. (_Terebro_, to pierce.) Shells which reside in
    holes pierced in rocks, wood, &c. by means of some corrosive secretion
    of the animal. _Ex._ Pholas, Teredo, &c.

    TEREBRATULA. Brug. (_Terebrans_, bored.) _Fam._ Brachiopoda,
    Lam.--_Order._ Palliobranchiata, Bl.--_Descr._ Inequivalve,
    equilateral, oval or sub-trigonal, ventricose or compressed, attached
    by a tendon passing through an opening in the dorsal, or upper and
    larger valve, the umbo of which advances beyond that of the other
    valve; hinge destitute of a ligament, with two teeth in the dorsal
    valve, locked into corresponding cavities in the ventral, or lower
    valve, and with two curious processes originating at the umbo of the
    lower valve, presenting, in some species, the appearance of fine
    winding tape, advancing towards the front of the valve, and again
    receding to the centre, where the ends unite; muscular impressions two,
    placed near the centre of each valve.--_Obs._ The Terebratulæ are
    included in the genus Anomia in the system of Linnæus. The recent
    species are not very numerous--they are found in all climates. The
    fossil species are more numerous than the recent ones, occurring in the
    secondary and tertiary formations. T. Psittacea, fig. 202.

    TEREDINA. (From Teredo.) _Fam._ Tubicolæ, Lam. Adesmacea, Bl.--_Descr._
    Valves equal, inequilateral, with prominent umbones, as it were
    soldered to the outside of the rounded end of a shelly tube, of which
    they form a part; aperture of the tube partly divided; a flat accessary
    valve placed on the umbones.--_Obs._ This genus, which is only known in
    a fossil state, is distinguished from Teredo, by the valves being fixed
    on the tube, and the tube being closed at one extremity. Fig. 46, 47,
    T. personata.

    TEREDO. Auct. (_A piercer._) _Fam._ Tubicolæ, Lam. Adesmacea,
    Bl.--_Descr._ Valves equal, inequilateral; presenting when closed, an
    orbicular figure, with a large angular opening in front, and a rounded
    opening at the back; placed at the anterior extremity of an irregular,
    flexuous, elongated tube, open at both ends; the anterior termination
    divided in a double aperture opened and closed at the will of the
    animal by two opercula.--_Obs._ This genus of Molluscous Animals, is
    remarkable for boring holes in wood, which are filled by their
    elongated tubes, and give it a honey-comb appearance. Fig. 48. T.
    Navalis. Fig. 49, a piece of bored wood.

    TERMINAL. When the umbones of a bivalve shell are placed at or near the
    extremity, as in Mytilus, fig. 158, Pinna, fig. 162, they are said to
    be _terminal_. The same term is also applied to the nucleus of an
    operculum, when it forms an extreme point, or is close to one of the
    edges.

    TESSELLATED. (Wrought in chequer-work). A term applied to the colouring
    of shells, when arranged in regular defined patches like a tessellated
    pavement.

    TESTACELLA. (_Testa_, a shell.) _Fam._ Limacinea, Lam. and
    Bl.--_Descr._ Haliotoid, compressed; aperture wide, oblique; columella
    flat, oblique; spire short, flat, consisting of less than two
    whorls.--_Obs._ This shell which is extremely small compared with the
    animal, is placed upon its back, near the posterior extremity. The
    animal is found in some of our gardens, and very much resembles the
    common garden slug. Fig. 261, T. Haliotoidea.

    TESTACEOUS. (_Testa_, a shell.) Shelly. Testaceous Mollusca, are soft
    animals having shells. A testaceous operculum is one composed of shelly
    matter.

    TETRACERA. Bl. The first family of the order Polybranchiata, Bl.
    containing no genera of testaceous mollusca.

    TEXTILIA. Sw. A sub-genus of Conus, consisting of Conus bullatus, &c.
    Sw. Malac. p. 312.

    TEXTULARIA. Defr. A genus of microscopic Foraminifera.

    THALAMUS. Montf. A genus described as resembling Conilites, but curved
    and granulated.

    THALLEPUS. Sw. A genus of "Aplysianiæ," Sw. thus described: "Body more
    slender and fusiform;" (than Aplysia,) "the lobes of the mantle short,
    and incapable of being used for swimming; tentacula two, large, ear
    shaped; eyes not visible. T. ornatus, _Sw._ Sp. Nov." Sw. p. 359.

    THALLICERA. Sw. A generic name under which Swainson distinguishes
    AMPULLARIA Avellana, Auct.

    THECIDIUM. (_Thecas_, a box.) _Fam._ Brachiopoda, Lam. _Order_,
    Palliobranchiata, Bl.--_Descr._ Lower valve concave, sub-trigonal, with
    the umbo produced into a triangular, slightly incurved beak, and with
    two short, pointed processes advancing from beneath the umbones; upper
    valve flat, rounded square, with a short, blunt appendage, formed to
    fit between the tooth-like process of the other valve; its inner
    surface ornamented with symmetrically curved ridges.

    THECOSOMATA. Bl. The first family of the order Aporobranchiata, Bl.
    containing the genera Hyalæa, Cleodora, Cymbulia, Pyrgo.

    THELICONUS. Sw. A sub-genus of Conus. Lardn. Cyclop. Malac. p. 312.

    THELIDOMUS. Sw. A generic name under which Swainson has described a
    division of the genus Helix, and which he has also used to designate a
    genus in the family of "Rotellinæ," founded upon an aggregate of loose
    particles collected and agglutinated in a spiral form by the larva of
    an insect. Sw. Malac. p. 330 and 353.

    THEMEON. Montf. A genus of microscopic Foraminifera.

    THEODOXUS. Montf. A division of the genus Nerita. Fig. 324, N.
    virginea.

    THETIS. Sow. (_A sea nymph._) A genus of fossil shells, described as
    resembling Mactra, but not having the internal ligament, and having
    several small, acuminated, cardinal teeth, but no lateral teeth. It
    resembles Tellina in some degree, but has not the posterior fold.

    THIARELLA. Sw. A sub-genus of Mitra, Lardn. Cyclop. Malac. p. 319.

    THRACIA. Leach. _Fam._ Lithophagidæ, Lam. Pyloridea, Bl. A genus
    described as intermediate between Anatina, and Mya, and in some degree
    resembling Corbula. T. corbuloides, fig. 93.

    THUNDER-STONES. One of the vulgar appellations which have been applied
    to shells of the genus Belemnites.

    THIATYRA. Leach. A genus composed of AMPHIDESMA _flexuosa_, Lam. and
    similar species, belonging more properly to the genus LUCINA.

    TIARA. Sw. A genus of "Mitranæ," Sw. thus described: "Aperture narrow,
    linear, or of equal breadth throughout; outer lip and base of the body
    whorl contracted, the former generally striated; an internal canal at
    the upper part of the aperture; shell (typically) turrited, and equally
    fusiform; representing the _Muricidæ_ and Cymbiola." Sw. Malac. p. 319.
    The principal difference between Tiara and Mitra appears to be that in
    the latter, the aperture is more linear and contracted in the centre.
    Mitra Episcopalis is an example.

    TINOPORUS. Montf. A genus of microscopic Foraminifera.

    TIRANITES. Montf. A division of the genus Baculites.

    TOMELLA. Sw. A genus of "Pleurotominæ," Sw. thus described: "Fusiform,
    smooth; the spire of very few whorls, and not longer than the channel;
    inner lip with a thick callosity at the top; the slit short and wide;
    lineata, En. Méth. 440, f. 2, clavicularis, Ib. f. 4. filosa. En. Méth.
    440, f. 6. lineolata. Ib. f. 11." Sw. p. 314.

    TOMOGERUS. Montf. ANASTOMA, Auct. Fig. 471.

    TONICHIA. Gray. Syn. B. M. p. 126. A genus composed of those species of
    Chiton which have the margin smooth.

    TORNATELLA. Auct. _Fam._ Plicacea, Lam.--_Descr._ Oval, spirally
    grooved; spire short, rather obtuse, consisting of few whorls; aperture
    long, narrow, rounded anteriorly; outer lip simple; inner lip thin,
    slightly spread, columella spiral, incrassated, confluent with the
    outer lip. The recent species are few. Several fossil species occur in
    London Clay, Inferior Oolite and Calcaire-grossièr. Monoptygma, Lea,
    resembles this genus, but has a fold on the inner lip. Fig. 343, T.
    solidula.

    TORTUOUS. (_Tortuosus_) Twisted. This adjective is sometimes applied as
    a specific name; as Arca tortuosa.

    TRACHELIPODA. Lam. ([Greek: trachêlos], _trachelos_, a neck; [Greek:
    poda], _poda_, foot.) The third order of the class Mollusca, in the
    system of Lamarck. The trachelipodous mollusca are described as having
    the posterior part of the body spirally twisted and separated from the
    foot; always enveloped in a shell. The foot is free, flat, attached to
    the base of the neck. Shell spiral, and enclosing the animal when at
    rest. This order contains the families, Colimacea, Lymnacea, Melaniana,
    Peristomiana, Neritacea, Janthinea, Macrostomata, Scalariana, Plicacea,
    Canalifera, Alata, Purpurifera, Columellaria, Convolutæ. The genera
    belonging to these families, are represented in the plates, fig. 264,
    to 462.

    TRANSVERSE. (Crosswise.) A shell is said to be transverse, when its
    width is greater than its length, that is, when it is longer from one
    side to the other than from the umbones to the ventral margins. The
    term is applied by some authors to express the direction of the lines
    of growth in bivalve shells, and the spiral lines in spiral shells. See
    CONCENTRIC.

    TRAPEZIUM. Meg. CYPRICARDIA, Lam.

    TRAPEZIFORM, or

    TRAPEZOID. ([Greek: trapezion], _trapezion_, _trapezium_; [Greek:
    eidos], _eidos_, form.) Having four unequal and unparallel sides. _Ex._
    Cucullæa, fig. 133.

    TRIBULUS. Klein. RICINULA, Lam.

    TRICHOTROPIS. Brod. and Sow. ([Greek: Trichos], _trichos_, hair;
    [Greek: tropis] _tropis_, keel.) _Fam._ Purpurifera, Lam.--_Descr._
    Turbinated, keeled, thin, umbilicated; aperture longer than the spire,
    entire; columella obliquely truncated; outer lip thin, sharp; epidermis
    horny, produced into long hairs at the angles of the shell; operculum
    horny, with the nucleus lateral.--_Obs._ Although the shells of this
    genus have something of the shape of Turbo, they are distinguished from
    that genus at once by the thinness of the shell. They are also known
    from Buccinum, by the absence of a canal. Only two or three species are
    known, which belong to the Northern and Arctic Oceans. T. bicarinata,
    fig. 429.

    TRIDACNA. Auct. _Fam._ Tridacnacea, Lam. Chamacea, Bl.--_Descr._
    Equivalve, regular, inequilateral, radiately ribbed, adorned on the
    ribs with vaulted foliations, waved at the margins, with a large,
    anterior hiatus close to the umbones, for the passage of a large
    byssus, by which the animal fixes itself to marine substances; hinge
    with a partly external ligament; two laminar teeth in one valve, one in
    the other.--_Obs._ The beautiful shells composing this genus are of a
    delicate white colour, tinged with buff. One species, the T. gigas,
    attains a remarkable size, measuring from two to three feet across, and
    weighing five hundred pounds. Tridacna is distinguished from Hippopus
    by the large opening in the hinge. T. elongata, fig. 157.

    TRIDACNACEA. Lam. A family belonging to the first section of the order
    Conchifera Dimyaria, Lam. described as regular, equivalve, solid, and
    which are remarkable for the deeply sinuated or undulated ventral
    margin. This family contains the genera:

        1. HIPPOPUS. Valves closed at or near the hinge. Fig. 156.

        2. TRIDACNA. An hiatus near the hinge. Fig. 157.

    TRIDENTATE. (_Tridentatus_.) Having three teeth, or salient points.
    _Ex._ Hyalæa tridentata, fig. 226.

    TRIGONA. Schum.? Triangular species of CYTHEREA, such as C. lævigata,
    Triplas corbicula, ventricosa, bicolor, &c. Fig. 117 _b._

    TRIGONACEA. Lam. A family belonging to the order Conchifera Dimyaria,
    containing the genera Trigonia and Castalia, the latter of which ought
    to be removed to the Nayades. Fig. 139, 140.

    TRIGONAL. Triangular, having three sides.

    TRIGONELLA. Humph. MACTRA, Auct.

    TRIGONIA. Brug. ([Greek: trigônon], _trigonon_, triangular.) _Fam._
    Trigonata, Lam. Camacea, Bl.--_Descr._ Equivalve, inequilateral,
    transverse, sub-trigonal, costated and granulated without, pearly and
    iridescent within, denticulated on the inner margin, rounded
    anteriorly, truncated posteriorly; hinge with four oblong, compressed,
    diverging teeth in one valve, receiving between their grooved sides,
    two similar teeth in the other; ligament external, thick; muscular
    impressions two in each valve.--_Obs._ Only one recent species of this
    marine genus is known, the T. pectinata, which comes from New Holland;
    and was formerly so rare, that a much worn odd valve has been sold for
    a considerable sum. It is of a brilliant pearly texture within, tinged
    with purple or golden brown. Fossil species occur in Lias, upper and
    lower Oolite, and Green-sand. T. Pectinata, fig. 139.

    TRIGONOSEMUS. König. A genus composed of species of TEREBRATULA, Auct.
    which have one valve produced into a beak, perforated, or as it were
    truncated at the apex. T. lyra, fig. 208, differing from Terebratula
    lyra, Lam.

    TRIGONOSTOMA. A sub-genus of Helix, with a trigonal aperture. Gray's
    Turton, p. 139.

    TRIGONOTRETA. König. A genus composed of species of Terebratula, Auct.
    which have the hinge of the larger valve produced into a triangular
    disc, divided by a triangular foramen in the centre. Spirifer, Sowerby,
    belongs to this genus. Fig. 214, 215.

    TRILOBATE. ([Greek: Treis] three; [Greek: lobos], division, lobe.)
    Divided into three lobes or principal parts. Ex. Malleus, Fig. 165.

    TRILOCULINA. D'Orbigny. A genus of microscopic Foraminifera.

    TRIPARTITE. (_Tripartitus_) composed of or divided into three separate
    parts.

    TRIPHORA, or TRISTOMA. Deshayes. A genus composed of small reversed
    species of CERITHIUM, Auct. which have the anterior canal closed at the
    anterior of the aperture, but opened at the extremity, and a small
    tubular opening on the upper part of the whorls, making three openings
    on the body whorl. This genus stands in the same relation to Cerithium
    as the Typhis to Murex. Fig. 375 in the old plates, and fig. in the new
    plates.

    TRIPLEX. Humph. MUREX, Linn.

    TRIPLODON. Spix. HYRIA, Auct.

    TRIPTERA. Quoy et Gaimard, CUVIERA, Fer. Described in the Voyage de la
    Coquille, and represented as a molluscous animal destitute of a shell.

    TRIQUETRA. Bl. Triangular species of VENUS Auct.

    TRISIS. Oken. ARCA tortuosa, Auct.

    TRISTOMA. Described as TRIPHORA.

    TRITON. Auct. _Fam._ Siphonostomata, Bl. Canalifera, Lam.--_Descr._
    Oblong or oval, thick, ribbed or tuberculated, with discontinuous
    varices placed at irregular distances; spire prominent, mammillated;
    aperture round or oval, terminating anteriorly in a generally long,
    slightly raised canal; columellar lip granulated or denticulated; outer
    lip thickened, reflected, generally denticulated within; epidermis
    rough; operculum horny.--_Obs._ However nearly allied the Tritons may
    appear to be to the Murices and Ranellæ there are still to be traced in
    the shells of each of those genera, several constant and well marked
    distinctions, by which they maybe at once recognized. In the Ranellæ,
    the varices run in two rows along the spire; in the Murices, they form
    three or more rows; but in the Tritons, they do not follow each other,
    _i.e._ they do not occur in the same part of each volution. The large
    species of Triton, are sometimes used as trumpets. The Tritons are
    brought from the Mediterranean, Ceylon, the East and West Indies, and
    South Seas. Fig. 398 to 401.

    TRITONIDEA. Sw. A genus of "Buccininæ," Sw. thus described: "Shell
    bucciniform, but the basal half is narrowed, and the middle more or
    less ventricose; spire and aperture equal. Pillar at the base with two
    or three obtuse and very transverse plaits, not well defined; outer lip
    internally crenated and with a superior siphon; inner lip wanting, or
    rudimentary." This genus is the same as the one first distinguished by
    Mr. Gray under the name of Pollia. We do not regret the discovery made
    by Mr. Swainson of that name being previously occupied for a genus of
    Lepidopterous Insects. Fig. 415, represents Tritonidea articularis.
    (Pollia, Gray.)

    TRIVIA. Gray. A genus composed of those small species of CYPRÆA, Auct.
    which are characterized by small ridges on the dorsal surface, and have
    the anterior of the columella internally concave and ribbed. C.
    Pediculus. Auct. fig. 449, 450.

    TROCHATELLA. Sw. A sub-genus of Helicinæ, consisting of those species
    which are acute and trochiform.

    TROCHIA. Sw. A genus of the family Buccininæ, thus described: "shape
    intermediate between Purpura and Buccinum; whorls separated by a deep
    groove; inner lip when young, depressed, when adult, thickened, convex
    and striated; basal canal very small. T. sulcatus. E. M. 422. f. 4."
    Sw. Malac. p. 300.

    TROCHIDON. Sw. A sub-genus of "Trochinæ," Sw. Lardn. Cyclop. Malac. p.
    351.

    TROCHILÆA. Sw.? PILEOLUS, Auct.

    TROCHURUS. Humph. MONODONTA. Lam.

    TROCHUS. Auct. (_A top._) _Fam._ Turbinacea, Lam. Goniostomata,
    Bl.--_Descr._ Turbinated, thick, striated, tuberculated or smooth;
    spire elevated, conical, consisting of numerous whorls; under surface
    discoid; aperture more or less depressed in an oblique direction,
    generally angular; columella arcuated, more or less prominent at its
    union with the outer lip, contiguous to the axis of the shell;
    operculum horny, orbicular, with numerous whorls.--_Obs._ Lamarck
    distinguished this genus from Turbo by the general form, which is more
    conical, and the aperture, which is angulated, while that of Turbo is
    rounded. Monodonta or Odontis is only separated on account of the notch
    at the termination of the columella. But these characters glide so
    imperceptibly from one genus to the other, that there is no line of
    demarcation to be found but in the operculum. Accordingly, Sowerby (in
    Gen. of Sh. 37.) has stated his reasons for considering as Trochi, all
    the species which have horny opercula; and as Turbines, all those which
    have testaceous opercula. Fig. 358 to 360. The Trochi are found in all
    climates.

    TROPÆUM. Sow. CRIOCERATITES.

    TROPHON. Montf. MUREX Magellanicus, Auct. and several other species
    which belong more properly to Fusus than to Murex.

    TRUMPET SHELL. A large species of Triton (variegatus), used by natives
    of South Sea Islands as a trumpet, to call warriors and herds of cattle
    together. It answers the purpose tolerably well, producing a very
    sonorous blast.

    TRUNCATED. (_truncus_, cut short.) Terminating abruptly, as it were cut
    short. _Ex._ Solenensis, fig. 60.

    TRUNCATULANA. D'Orb. A genus of microscopic Foraminifera.

    TRUNCATELLA. Risso. A genus composed of several species of land shells
    which have been confounded by some authors with Cyclostoma. The genus
    is thus described: "Shell turriculated, cylindrical, decollated or
    truncated at the apex, no epidermis; aperture oval, short, with lips
    continuous, simple." _Ex._ Truncatella truncatulina, Lowe, Zool. Journ.
    t. 5. p. 80. Our plates, fig. 520, 521. It is found on the shores of
    Britain, the Mediterranean, and West Indies.

    TUBA. Lea. A genus of small fossil shells, described as resembling
    Turbo, but with the aperture more like that of Melania. Lea. Contrib.
    Geol.

    TUBERCLE. (_tuberculus._) A small swelling excrescence, or knob.

    TUBERCULATED. Having a number of small lumps or pimples, as Turrilites,
    fig. 483.

    TUBICINELLA. Lam. (_Tubicen_, a trumpeter.) _Order_, Sessile
    Cirripedes, Lam.--_Descr._ A cylindrical tube, composed of six
    elongated valves jointed together side by side, striated
    longitudinally, surrounded by concentric rings; aperture circular,
    enclosed by an operculum of four valves, placed perpendicularly in an
    epiphragm.--_Obs._ The Tubicinellæ are found with nearly the whole
    shell buried in the thick skin of the whale. T. Balænarum.

    TUBICOLARIA. Lam. (_Tuba_, a tube; _cola_, an inhabitant.) A family of
    the order Conchifera Dimyaria, Lam. consisting of bivalves soldered as
    it were within, or connected with, a testaceous tube. The genera
    contained in this family may be thus distinguished.

        1. ASPERGILLUM. Valves fixed, tube perforated and fringed. Fig. 44.

        2. TEREDINA. Valves fixed, prominent, tube closed at one end.
        Fossil. Fig. 46, 47.

        3. CLAVAGELLA. One valve fixed, the other free. Fig. 45.

        4. TEREDO. Both valves free, tube open at both ends. Fig. 48, 49.

        5. FISTULANA. Valves free, tube closed at one end, straight, long.
        Fig. 53, 54.

        6. GASTROCHÆNA. Valves free, tube closed at one end, short,
        bulbous. Fig. 52.

    TUBIVALVES. Bl. Shells composed of two valves connected in a tube,
    corresponding with the family Tubicolæ of Lamarck.

    TULIPARIA. Sw. A sub-genus of "Coronaxis," Sw. Lardn. Cyclop. Malac. p.
    311.

    TURBINACEA. Bl. The sixth family of Polythalamacea, Bl. containing the
    genera Cibicides and Rosallites, microscopic Foraminifera.

    TURBINACEA. Lam. A family of the first section of the order
    Trachelipoda, Lam. containing the following genera.

        1. SOLARIUM. With umbilicus reaching to the apex; including
        _Bifrontia_ and _Orbis_. Fig. 353 to 356.

        2. ROTELLA. A callosity on the under side. Fig. 357.

        3. PHASIANELLA. Oval; operculum shelly. Fig. 367.

        4. PLANAXIS. Columellar lip flat; aperture notched. Fig. 365.

        5. TURBO. Top-shaped; mouth generally round; operculum shelly. Fig.
        368.

        6. TROCHUS. Top-shaped; mouth generally angulated; operculum horny,
        consisting of many whorls; including _Elenchus_. Fig. 358, 359,
        361.

        7. MARGARITA. Operculum horny, consisting of few whorls; pearly.
        Fig. 362.

        8. LITTORINA. Similar, not pearly; including _Assiminnea_. Fig.
        363, 363*.

        9. PHORUS. Attaching dead shells, stones, &c. Fig. 360.

        10. MONODONTA or ODONTIS. A notch and prominent point at the lower
        part of the aperture. Fig. 366.

        11. LACUNA. With an umbilicus. Fig. 364.

        12. TURRITELLA. Elongated, screw-shaped. Fig. 369 to 371.

    TURBINATED. (_Turbo_, a top,) Top-shaped. The term is applied generally
    to those shells which are large at one extremity, and narrow to a point
    at the other. _Ex._ Trochus, fig. 358; Turbinellus, fig. 382.

    TURBINELLUS. Auct. (_A little top._) _Fam._ Canalifera, Lam.
    Siphonostomata, Bl.--_Descr._ Turbinated, thick, wide near the apex,
    generally tuberculated; spire short, depressed, mammillated; aperture
    rather narrow, terminating anteriorly in an open canal; outer lip
    thickened within; columella having from three to five prominent,
    compressed, transverse folds. The species of this genus are mostly
    tropical.--_Obs._ The Turbinelli are a well marked genus of marine
    shells, the species of which are numerous. No fossil species are known.
    The genus Cancellaria makes the nearest approach to Turbinellus in some
    characters, but may be distinguished by the roundness of its form, the
    raised lines inside the outer lip, and the obliquity of the folds on
    the columella. Fig. 382 to 384.

    TURBO. Auct. (_A top._) _Fam._ Cricostomata, Bl. Turbinacea,
    Lam.--_Descr._ Turbinated, solid, ventricose, generally grooved or
    tuberculated; spire short, pointed; aperture generally rounded,
    sub-effuse anteriorly, entire; operculum shelly, solid, incrassated on
    the outer side, horny and sub-spiral on the inner side. The Turbines
    are mostly tropical.--_Obs._ The only certain means of distinguishing
    this extensive genus of marine shells from Trochus, is the operculum,
    which in the latter genus is horny, spiral, and composed of a great
    number of whorls. The Trochi, however, are in general more conical, and
    flatter at the under side of the whorls, and this constitutes Lamarck's
    distinction between the genera. T. setosus, fig. 368.

    TURGID. (_Turgidus._) Puffed up, swollen, inflated. This term is
    applied synonymously with Ventricose.

    TURRICULA. Humph. MELANIA, Auct.

    TURRICULACEA. Bl. The seventh family of the Order Polythalamacea, Bl.
    containing the genus Turrilites, fig. 483.

    TURRILITES. Lam. (_Turris_, a tower; [Greek: lithos], a stone.) _Fam._
    Turriculacea, Lam. Ammonacea, Bl.--_Descr._ Chambered, turrited,
    spiral; septa sinuous and lobate, perforated by a siphon; aperture
    rounded, with the outer lip expanded. This genus, which is
    distinguished from the other Ammonacea by having the spire produced,
    _i. e._ not being convolute, consists of several species, occurring
    only in chalk-marl. Fig. 483.

    TURRIS. Montf. A genus composed of those species of MITRA, Auct. which
    have the whorls angulated, with the aperture lengthened and undulated.

    TURRITED. The spire of an univalve shell is said to be _turrited_ when
    the whorls of which it is composed are regulated so as to have the
    appearance of little turrets rising above each other, as in Mitra, fig.
    431.

    TURRITELLA. Lam. (_A little tower._) _Fam._ Turbinacea, Lam.
    Cricostomata, Bl.--_Descr._ Turrited, elongated, generally grooved
    spirally; spire pointed, consisting of numerous whorls; aperture
    rounded or angulated; inner and outer lips thin, confluent anteriorly;
    operculum horny.--_Obs._ The shells composing this well defined genus,
    are commonly called screws, a name to which the spiral grooves of most
    of the species seems to entitle them. Fig. 370, T. imbricata.

    TYMPANOSTOMA. Schum. (_Timbrel mouth._) POTAMIS, Brongn.

    TYPHIS. Montf. A genus composed of MUREX tubifer, Auct. and other
    similar species, which have the canal closed and a perforated tube
    between each varix on the angulated part of the whorls. Besides the
    fossil species originally described, there are now five species known,
    which are figured in part 200, of the Conchological Illustrations by
    the Author. Typhis tubifer, fig. 397.

    ULTIMUS. Montf. (_The last._) A genus composed of OVULUM gibbosum,
    Auct. fig. 443, and other species in which the canals are not
    distinctly defined, nor elongated. This fanciful name is given to the
    genus on account of its being described in the last page of the book.

    UMBILICATED. (_Umbilicatus._) Having an umbilicus, as Nautilus
    umbilicatus.

    UMBILICUS. (_A navel._) The hollow formed in spiral shells when the
    inner side of the volutions do not join each other, so that the axis is
    hollow. The umbilicus is marked with the letter u in Helix algira, fig.
    279. The term is also used to express any small, neat, rounded hollow.

    UMBO. (_The boss of a buckler or shield._) The point of a bivalve shell
    above the hinge, which constitutes the apex or nucleus of each valve,
    from which the longitudinal rays diverge, and the lines of growth,
    commencing at the minutest circle, descend in gradually enlarging
    concentric layers to the outer margin. The umbones will be marked with
    the letter _u_, in Cytherea, fig. 117.

    UMBRELLA. (_A little shade._) _Fam._ Semiphyllidiana, Lam. Patelloidea,
    Bl.--_Descr._ Patelliform, sub-orbicular, compressed, rather irregular;
    apex slightly raised, placed near the centre; margin acute; internal
    surface with a central, callous, coloured disc, surrounded by a
    continuous, irregular muscular impression.--_Obs._ This genus is known
    from Patella, by its continuous muscular impression. It is commonly
    called the Chinese Umbrella shell. There are but two species at present
    known; the U. Mediterranea, and the U. Indica, fig. 233.

    UNDATED. (_Unda_, a wave.) Waved.

    UNDULATED. (_Undulatus._) Minutely waved.

    UNGUICULATED. (_Unguis_, a nail or hoof.) An unguiculated operculum is
    one in which the layers are disposed laterally, and the nucleus
    constitutes part of the outer edge.

    UNGULINA. Daud. (_Ungula_, a nail or claw.) _Fam._ Mactracea, Lam.
    Conchacea, Bl.--_Descr._ Equivalve, sub-orbicular, sub-equilateral,
    with margins entire, simple, closed all round; hinge with one short,
    sub-divided cardinal tooth in each valve, and a very minute additional
    tooth in one valve, an oblong ligamentary pit divided into two
    portions, one of which receives the cartilage, the external ligament is
    immediately below the umbones; muscular impressions, two in each valve,
    oblong; impression of the mantle entire. U. transversa, fig. 88. Coast
    of Africa.

    UNI-AURICULATED. Having one AURICLE. See AURICULATED.

    UNICORNUS. Montf. MONOCEROS, Auct.

    UNIO. (_A pearl._) _Fam._ Nayades, Lam. Submytilacea, Bl.--_Descr._
    Inequilateral, equivalve, regular, free, pearly within, covered by a
    smooth epidermis without; umbones prominent, generally corroded;
    muscular impressions two in each valve, lateral, distant; the anterior
    composed of several small divisions; hinge varying in age, species, and
    individuals.--_Obs._ The above description is framed so as to include
    all the genera of the Lamarckian Nayades, together with Castalia, which
    are placed in the family Trigonacea, they are all fresh-water shells,
    commonly called fresh-water muscles. The distinctions of the various
    genera into which they have been divided, will be found in their
    respective places, and under the name Nayades. They are all represented
    in figures 140 to 152. Of these fig. 145 to 148, are more generally
    considered as forming the genus Unio.

    UNIOPSIS. Sw. A sub-genus of Alasmodon. Sw. p. 382.

    UNIVALVE. (_Unus_, one; _valva_, valve.) A shell consisting of a single
    piece, as distinguished from Bivalves and Multivalves, which are
    composed of two or more principal pieces. Spiral shells having an
    operculum, are called sub-bivalves by some authors.

    UPPER-VALVE. The free valve in attached bivalves.

    UVIGERINA. D'Orb. A genus of microscopic Foraminifera.

    VAGINA. Megerle. SOLEN _vagina_, Auct.

    VAGINULA. (_A little sheath, the husk of corn._) _Class_, Pteropoda,
    Lam.--_Descr._ Pyramidal, slightly inflated in the centre, thin,
    fragile; aperture oblong, with the edges turned slightly
    outwards.--_Obs._ The little shells of this genus, which are only known
    in a fossil state, differ from Cuvieria in being pointed at the
    extremity. Found in the tertiary beds of Bordeaux. V. Daudinii, fig.
    225.

    VAGINULINA. D'Orb. A genus of microscopic Foraminifera.

    VALVATA. Müll. _Fam._ Peristomata, Lam. Cricostomata, Bl.--_Descr._
    Thin, turbinated; spire short, composed of from three to six rounded
    whorls; aperture circular; peritreme acute, entire; operculum horny,
    spiral.--_Obs._ This genus of small shells resembles Cyclostoma, from
    which the recent species may be known by the horny texture of the
    external surface, being fresh-water shells. The fossils of course
    belong to the fresh-water formations. V. piscinalis, fig. 322. Europe
    and North America.

    VALVES. (_Valva_, a door, a folding piece.) The two pieces composing a
    bivalve shell, which close upon each other, turning upon a hinge
    consisting of a ligament, cartilage, and teeth. See BIVALVE,
    MULTIVALVE, and UNIVALVE.

    VALVULINA. D'Orb. A genus of microscopic Foraminifera.

    VARIX. (_A swelling vein._) A varix is formed on the outer surface of a
    spiral shell, by the thickened, reflected edge of a former aperture,
    after fresh deposits of testaceous matter have increased the size by
    adding to the growth of the shell beyond it. In this manner there are
    frequently many varices, or edges of former apertures, in various parts
    of the spire and the body whorl. They are sometimes placed at regular
    distances from each other, as in Harpa, fig. 419; sometimes
    _continuous_, as in Ranella, fig. 394; sometimes _discontinuous_, as in
    Triton, fig. 398; sometimes _ramose_, as in Murex, fig. 395; sometimes
    _simple_, as in Scalaria, fig. 351; sometimes _spinose_, as in Murex
    spinosus. The term _varix_ has also been applied to any swelling ridge,
    such as that on the lower part of the columella of Ancillaria, fig.
    456.

    VELATES. Montf. NERITINA perversa, Auct. Fig. 326.

    VELLETIA. Gray? A genus described as differing from ANCYLUS in being
    dextral. VELLETIA lacustris, ANCYLUS lacustris, Auct. fig. Sowerby Gen.
    fig. 2.

    VELUTINA. Auct. _Fam._ Macrostomata, Lam.--_Descr._ Sub-globose,
    covered with a velvety epidermis; spire short, composed of two rapidly
    enlarged ventricose whorls; aperture large, sub-ovate; peritreme thin,
    entire, separated from the last whorl; columella tortuous,
    thin.--_Obs._ This shell does not resemble any other genus in the
    family. Fig. 337. Northern Seas.

    VENERICARDIA. Lam. A genus composed of the shorter species of Cardita.

    VENERIRUPIS. Lam. (From _Venus_ and _rupis_, a rock.) The oblong
    species of Venus Auct. which live in cavities of rocks and stones. This
    genus is united by Sowerby with some other species of Venus under the
    name Pullastra. V. Vulgaris, fig. 97.

    VENTRAL. (_Venter_, the belly.) The margin of a bivalve shell opposite
    the hinge. The under valve in Brachiopodous bivalves is the ventral
    valve. The ventral surface of an univalve spiral shell is that which
    faces the observer when the aperture is placed towards him. The ventral
    part of the whorls of symmetrical convolute shells, is the inner part,
    that which is nearest to the spire.

    VENTRAL SIPHON. In symmetrical convolute univalves, is one placed near
    the inner edge of the whorls.

    VENTRICOSE. (_Ventricosus._) Swelled, rounded out, (_bombé Fr._) as
    Harpa ventricosa, fig. 419.

    VENUS. Auct. (_Goddess of Beauty._) _Fam._ Marine Conchacea, Lam.
    Conchacea, Bl.--_Descr._ Equivalve, inequilateral, sub-globose,
    sub-ovate, transverse, externally rugose, striated, ribbed, cancellated
    or smooth; margins entire, simple, close; hinge with three more or less
    distinct cardinal teeth, diverging from the umbones in each valve;
    muscular impressions two, lateral, distant; palleal impressions
    sinuated posteriorly; ligament external.--_Obs._ This extensive genus,
    including some bivalves of splendour and beauty, justifying the name
    given to it, may be known from Cytherea by the absence of a lateral
    tooth, which is found near the cardinal teeth in the latter. Artemis is
    distinguished not only by its beautiful form, but by the deep angular
    sinus in the palleal impression. Fig. 119, 119 a. Found mostly in
    temperate and tropical climates.

    VERMETUS. Adanson. _Fam._ Scalariana, Lam. Cricostomata, Bl.--_Descr._
    Spiral at the apex, irregularly twisted towards the aperture; aperture
    round, small.--_Obs._ This shell resembles the Serpulæ in general
    appearance, although it is regularly spiral near the apex. The animal
    is known to be a true mollusc, rather nearly allied to that of the
    genus Dentalium, which is also placed wrongly in the Lamarckian system.
    Vermetus Lumbricalis, fig. 345. Coast of Africa.

    VERMICULAR. (_Vermicularis._) Worm-shaped, tubular, serpentine. _Ex._
    Vermilia triquetra, fig. 7.

    VERMICULARIA. Lam. VERMETUS, Adanson; afterwards VERMETUS, Lam.

    VERMILIA. Lam. A genus composed of species of Serpula, which are
    attached by the whole length of the shell, no part being free. Vermilia
    triquetra, fig. 7.

    VERTEBRALINA. D'Orb. A genus of microscopic Foraminifera.

    VERTEX. Apex.

    VERTIGO. Müll. _Fam._ Colimacea, Lam.--_Descr._ Cylindrically fusiform,
    sinistral, hyaline; aperture marginated, sinuated, denticulated on the
    inner edge; peristome sub-reflected.--_Obs._ This genus of minute land
    shells, resembles Pupa, but is a reversed, hyaline shell. Vertigo
    pusilla, fig. 293. Europe.

    VERRUCA. Schum. CLITIA, Leach.

    VESICA. Sw. A sub-genus of Bulinus, Sw. p. 360.

    VEXILLA. Sw. A genus of "Nassinæ," Sw. thus described: "General shape
    of _Purpura_, the inner lip flattened and depressed; the outer, when
    adult, thickened, inflected and toothed; aperture wide; picta _Sw._
    Chem. pl. 157, f. 1504-5." Sw. Malac. p. 300.

    VIRGULINA. D'Orb. A genus of microscopic Foraminifera.

    VITRELLA. Sw. A sub-genus of "Bullinæ," Sw. Lardn. Cyclop. Malac. p.
    360.

    VITRINA. Drap. (_Vitreus_, glassy.) _Fam._ Limacinea, Lam. and
    Bl.--_Descr._ Ovate, thin, glassy, fragile; spire short; last whorl
    large; aperture wide, transverse; peritreme simple; columella spiral,
    linear.--_Obs._ This genus of land-shells is not known in a fossil
    state. The recent species are found among moss and grass, in shady
    situations. De Ferussac has divided this genus into Helicolimax, fig.
    263, and Helixarion, fig. 262.

    VITULARIA. Sw. A genus of "Muricinæ," Sw. thus described: "General
    habit of _Muricidea_, but the inner lip is depressed and flattened as
    in the _Purpurinæ_; varices simple, nearly obsolete. Tuberculata, Sw.
    En. M. 419. fig. 1. (_Murex vitulinus_, Auct.)" Sw. p. 297.

    VIVIPARA. A generic name given by Montfort, and retained by some
    authors for PALUDINA, Lam. on account of the animals being
    _viviparous_, i. e. the young being perfectly formed before they leave
    the ovaries.

    VIVIPAROUS. See VIVIPARA.

    VOLUTA. Auct. (_Volvo_, to revolve.) _Fam._ Columellaria, Lam.
    Angyostomata, Bl.--_Descr._ Sub-ovate, rather angulated, thick,
    generally tuberculated, smooth; spire short, conical, with a
    mammillated apex; aperture generally angulated, large, terminating
    anteriorly in a deep notch; columella smooth, with several plaits, of
    which the lowest is the largest; outer lip thickened within.--_Obs._
    The genus Voluta, as left by Linnæus, is only characterized by the
    folds on the columella, and includes many shells which, although they
    agree in this respect with the genus, are yet quite opposite to each
    other in all other characters. Thus the Auriculæ, which are land
    shells, and have the aperture entire, are mixed up with others which
    are marine, and have a canal, as Turbinellæ, and the Fasciolariæ, and
    others which have merely a notch, as the true Volutes. This genus, as
    it is circumscribed at present, includes a great number of beautiful
    shells, most of which are rich in colouring. CYMBA and MELO have been
    separated by Mr. Broderip from the genus VOLUTA of Lamarck, for reasons
    stated in their respective descriptions. Fig. 443.

    VOLVARIA. Lam. (_Volva_, a shuttle.) _Fam._ Columellaria,
    Lam.--_Descr._ Cylindrical, convolute, spirally striated; spire very
    short, nearly hidden; aperture narrow, as long as the whole shell;
    columella with three oblique plaits; outer lip dentated.--_Obs._ The
    Volvaria are only known in a fossil state, and resemble some species of
    Bulla in general form, but are distinguished by the plaits on the
    columella. Fig. 439, V. concinna.

    VOLUTELLA. Sw. (_A little volute._) A genus composed of those species
    of MARGINELLA, Auct. which have the spire concealed, and the aperture
    smooth within. Fig. 438, PERSICULA of Schumacher.

    VOLUTILITHES. Sw. (_Voluta_, and [Greek: lithos], _lithos_, a stone.) A
    genus composed of some fossil species of Voluta, which have the plaits
    on the pillar generally numerous, indistinct, and sometimes wanting
    altogether, with a pointed spire. Fig. 436, V. spinosa.

    VOLUTION. See WHORL.

    VORTICIALIS. Lam. A genus of microscopic Foraminifera.

    VULSELLA. Lam. (_A little tongue._) _Fam._ Ostracea, Lau. Margaritacea,
    Bl.--_Descr._ Equivalve, irregular, longitudinal, compressed, oblong;
    umbones separated by a slight area in both valves; hinge with a large
    pit in the centre, containing the cartilage, the ligament being spread
    over the areas; muscular impressions, one on each valve, sub-central,
    oblong.--_Obs._ This genus differs from Ostræa in the equality of the
    valves, and in having a hollow pit in the hinge for the cartilage.
    Vulsella lingulata, fig. 185.

    WATERING-POT. Aspergillum, fig. 44, commonly so called on account of
    the resemblance of its perforated termination to that of the spout of a
    watering-pot.

    WENTLE TRAP. Scalaria pretiosa, commonly so called.

    WHORL. A complete turn or revolution round the imaginary axis of a
    spiral shell. The last whorl is called the _body-whorl_. The whorls are
    described as _non-contiguous_, when they do not touch each other;
    _continuous_, in the opposite case. _Depressed_ when they are flat.
    They are _angulated_, _heeled_, or coronated; _distinct_, or
    indistinct. They are sometimes, as in Cypræa, hidden by the last whorl.

    XYLOPHAGA. Sow. ([Greek: xulon], _zylon_, wood; [Greek: phagô],
    _phago_, to eat.) _Fam._ Tubiscolæ, Lam.--_Descr._ Equivalve, globose,
    closed at the back; with a large, angular hiatus in front; hinge with a
    small curved tooth advancing from beneath the umbones in each
    valve.--_Obs._ This shell, which is found in a cylindrical cavity,
    eaten in wood by the animal, resembles Teredo, but has not the shelly
    tube, nor the posterior hiatus. X. dorsalis, fig. 50, 51.

    XYLOTRYA. Leach. XYLOPHAGA, Sow.

    ZONITES. Montf. A genus formed of Helix Algira, and other similar
    species with depressed spires and large umbilici; included in the
    sub-genus Helicella. Fig. 279.

    ZUA. Leach. A genus described as differing from Bulinus in having a
    polished epidermis, and a thickened, not reflected lip. Zua lubrica, B.
    lubricus, Auct.

    ZURAMA. Leach. A sub-genus of Helix. H. pulchella, Auct. Gray's Turton,
    p. 41.

       *       *       *       *       *


EXPLANATION OF PLATES,

AND SYSTEMATIC VIEW OF THE

LAMARCKIAN ARRANGEMENT.

         _Class_, ANNELIDES.
         _Order_, SEDENTARIA.
         _Fam._ Dorsalia.

  FIG.

    1.   Siliquaria anguina. Agathirses, Montf.

         _Fam._ Maldania.

    2.   Dentalium octogonum.

    3.   Pharetrium fragile, with the outer tube broken.

         _Fam._ Serpulacea.

    4.   Serpula bicarinata.

    5.   Spirorbis Nautiloides, on sea-weed.

    6.   Galeolaria decumbens, on a Conia.

    7.   Vermilia triquetra.

    8.   Spiroglyphus, on a portion of Patella.

    9.   Magilus antiquus, old shell. Campulotus, Guild. (from Guerin.)

   10.   The same, in a young state.

   11.   Leptoconchus striatus.

   12.   Stylifer astericola.

   13.   The same, in a portion of Star-fish.

         _Class_, CIRRIPEDES.
         _Order_, SESSILE CIRRIPEDES

   14.   Tubicinella Balænarum.

   15.   Coronula Testudinaria. Chelonobia, Leach, Astrolepas, Klein.

   16.   ---- Balænaris. Cetopirus, Ranz.

   17.   ---- diadema. Diadema, Ranz.

   18.   Chthalamus, Ranz. (from Blainville.)

   19.   Platylepas pulchra, Leach. One valve separate, showing the inside.

   20.   Clitia Verruca, Leach. Octhosia, Ranz. Verruca, Schum.

   21.   Conia porosa. Teraclita, Schum.

   22.   Elminius Leachii.

   23.   Catophragmus imbricatus, (from Sowerby's Genera.)

   24.   Octomeris angulosus, (from Sow. Gen.)

   25.   Balanus tintinnabulum.

   26.   ---- Montagui. Acasta, Leach.

   27.   ---- galeatus, Conoplæa, Say.

   28.   Creusia gregaria. _b._ showing the internal structure.

   29.   Nobia grandis.

   30.   Savignium crenatum.   }
                               }
   31.   Pyrgoma cancellata.   }   Pyrgoma, Auct.
                               }
   32.   Adna Anglicum.        }
                               }
   33.   Megatrema semicostata.}

         _Order_, PEDUNCULATED CIRRIPEDES.

   34.   Pentelasmis lævis. Antifa, Lam. a. anterior.

   35.   Scalpellum vulgare.

   36.   Smilium Peronii.

   37.   Pollicipes polymeus. Ramphidoma, Schum.

   37*.  Pollicipes mitellus. Capitulum, Klein.

   38.   Brismæus Rhophodius.

   39.   Lithotrya dorsalis. Absia, Leach, Litholepas, Bl.

   40.   Ibla Cuvieriana.

   41.   Heptalasmis Warwickii. Octolasmis, Gray.

   42.   Cineras vittatus.

   43.   Otion Cuvieri.

         _Class_, CONCHIFERA.
         _Order_, C. DIMYARIA.
         _Fam._ Tubicolaria.

   44.   Aspergillum vaginiferum. Penicillus, Brug.

   45.   Clavagella, a fossil species.

   46.   Teredina personata.

   47.   Lignite, pierced by Teredinæ.

   48.   Teredo navalis; _a_, tube (from Sowerby's Genera.)

   49.   Wood bored by Teredo.

   50.   Xylophaga dorsalis. Xylotrya, Leach.

   51.   The same, in wood.
         (This would be more properly placed in Pholadaria.)

   52.   Gastrochæna Modiolina, in the tube (from Sowerby's Genera.)

   53.   Fistulana Clava.  }
                           }   (From Sowerby's Genera.)
   54.   Tube of the same. }

         _Fam._ Pholadaria.

   55.   Pholas Dactylus; _a_, plates of the hinge.

   56.   ---- papyracea. Pholadidæa.

   57.   Pholadomya Candida.

   58.   Galeomma Turtoni.

   59.   Front view of the same.

         (Here Xylophaga should be placed, see Tubicolaria.)

         _Fam._ Solenacea.

   60.   Solen ensis. Ensis, Schum. Ensatella, Sw.

   61.   Solen radiatus. Solenocurtus, Bl. Leguminaria, Schum. Siliqua,
           Megerle.

   62.   Lepton squamosum. (from Turton.)

   63.   Novaculina gangetica.

   64.   Glanconome Chinensis.

   65.   Panopæa Australis.        }
                                   }    (From Sowerby's Genera.)
   66.   Hinge of Panopæa Faujasii.}

   67.   Glycimeris Siliqua.

   68.   Solenimya Mediterranea.

         _Fam._ Myaria.

   69.   Anatina rostrata. Auriscalpium, Megerle.

   70.   Anatinella Sibbaldii.

   71.   Mya truncata.

   72.   Periploma inæquivalvis. Osteodesma, Desh. _a_, bone of the
           hinge, (from Blainville.)

   73.   Myochama anomioides; lower valve with clavicle, and hinge of
           upper valve.

   74.   External view of the same, attached to a Trigonia.

   75.   Cleidothærus Chamoides, attached valve.

   76.   Upper valve of the same, with the clavicle.

         _Fam._ Mactracea.

   77.   Lutraria papyracea. Ligula, Leach. Carinella, Adans.

   78.   ---- Solenoides. Cutellus ----?

   79.   Mactra Stultorum.

   80.   ---- plicataria. Spisula? Gray.

   81.   ---- Spengleri. Schizodesma, Gray.

   82.   ---- bicolor. Mulinia, Gray.

   83.   Gnathodon cuneatus. Clathodon, Conrad.

   84.   Crassatella rostrata.

   85.   Amphidesma reticulatum.

   86.   Erycina plebeja. Mesodesma, Desh.

   87.   Cuming mutica.

   88.   Ungulina transversa, (from Sowerby's genera.)

         _Fam._ Corbulacea.

   89.   Corbula nucleus.

   90.   Pandora rostrata.

         _Fam._ Lithophagidæ.

   91.   Petricola Roccellaria.

   92.   ---- Carditoidea. Coralliophaga, Bl.

   93.   Thracia corbuloides.

   94.   Saxicava rugosa.

   95.   Hiatella biaperta.

   96.   Sphænia Binghamii.

   97.   Venerirupis vulgaris.

         _Fam._ Nymphacea.

   98.   Sanguinolaria rosea. Lobaria, Schum.

   99.   ---- Diphos. Soletellina, Bl.

  100.   Psammobia Ferroensis. Gari, Schum.

  101.   Corbis fimbriata. Fimbria, Megerle.

  102.   Grateloupia Moulinsii. (from Lea.)

  103.   Egeria triangulata, (from Lea.)

  104.   Lucina tigerina.

  105.   Tellina radiata.

  106.   ---- lingua-felis; _a_, showing the fold in the ventral
           margin.

  107.   Tellinides rosea.

  108.   Donax cuneatus.

  109.   Capsa Braziliensis, young.

  110.   Astarte Danmoniensis. Crassina, Lam.

         Fluviatile Conchacea.

  111.   Cyclas rivicola. Cornea, Megerle.

  112.   Pisidium amnicum. Pisum, Megerle.

  113.   Cyrena fuscata. Corbicula, Megerle.

  114.   Cyrenoides Dupontia.

  115.   Potamophila radiata. Galathæa, Lam. _v._ ventral margin.

         Marine Conchacea.

  116.   Cyprina vulgaris. Arctica, Schum.

  117.   Cythera Meretrix; _e._ escutcheon.

  117 _a._ C. Meroe; _Gen._ Meroe.

  117 _b._ C. Tripla; _Gen._ Trigona.

  117 _c._ C. maculata; _Gen._ Chione.

  117 _d._ C. Castrensis; _Gen._ Circe.

  118.   Artemis lincta; _s_, sinus in the Palleal impression.

  119.   Venus cancellata. Antigona, Schum. _a._ anterior; _p._
           posterior; _c._ cardinal teeth.

  119 _a._ V. Verrucosa. Dosina, Schum.

  120.   Pullastra Textile.

         _Fam._ Cardiacea.

  121.   Venericardia, recent species, resembling V. planicostata, Lam.

  122.   Cardium Dionæum. Cardissa, Sw. Hemicardium, Nonnull.

  123.   ---- angulatum.

  123*.  ---- Greenlandicum. Aphrodita, Lea, Acardo, Sw.

  123**. --- hemicardium. _Gen._ Hemicardum.

  124.   Cardita calyculata.

  125.   Cypricardia angulata.

  126.   Isocardia Moltkiana.

  127.   Megalodon cucullatus, (from Sow. Min. Con.)

  128.   Hippagus Isocardioides, (from Lea.)

  129.   Hippopodium ponderosum, (from Sow. Min. Con.)

  130.   Pachymya gigas, (from Sow. Min. Con.)

         _Fam._ Arcacea.

  131.   Arca antiquata.

  132.   Bysso-arca Noæ.

  133.   Cucullæa auriculifera, (from Sowerby's Genera.)

  134.   Pectunculus pilosus.

  135.   Myopara costata, (from Lea.)

  136.   Crenella.

  137.   Nucula margaritacea, three views.

  138.   Solenella Norrissii.

         _Fam._ Trigonacea.

  139.   Trigonia pectinata.

  140.   Castalia ambigua. Tetraplodon pectinatus, Spix.

         _Fam._ Nayades.

  141.   Alasmodon complanatus, Say. Margaritana, Schum.

  142.   Dipsas plicatus, Leach. Cristaria, Schum.

  143.   Hyria corrugata, Lam. Paxyodon, Schum. Triplodon.

  144.   Syrmatophora, Sow. Prisodon, Schum. Diplodon, Spix.

  145.   Unio littoralis, Lam. Mysca ovata, Turton.

  147.   ---- Alatus. Symphynota, Lea.

  148.   ---- Atratus, Lam. Naia, Sw.

  149.   Monocondylæa Paraguayana.

  150.   Iridina elongata. Pleiodon, Conrad.       } Platiris, Lea.
                                                   }
  151.   Mycetopus solenoides, D'Orb. Spatha, Lea. }

  152.   Anodon Cataractus.

         _Fam._ Chamacea.

  153.   Chama Lazarus. Jataronus, Adanson.

  154.   Diceras perversum, (from Sowerby's Genera.)

  155.   Etheria semilunata.

         _Order_, MONOMYARIA.
         _Fam._ Tridacnacea.

  156.   Hippopus maculatus.

  157.   Tridacna elongata.

         _Fam._ Mytilacea.

  158.   Mytilus achatinus.

  159.   ---- polymorphus. Dreissina.

  160.   Modiola Tulipa.

  161.   Lithodomus Dactylus.

  162.   Pinna saccata.

         _Fam._ Malleacea.

  163.   Avicula Hirundo.

  164.   ---- margaritifera. Meleagrina, Lam.

  165.   Malleus Vulgaris. Himantopoda, Schum.

  166.   Perna Ephippium.

  167.   Catillus Lamarckii. Inoceramus, Sow. (from Blainville.)

  168.   Crenatula mytoloides.  }
                                }
  169.   Gervillia aviculoides. } (from Sowerby's Genera.)
                                }
  170.   Pulvinites Adansonii.  }

         _Fam._ Pectinides.

  171.   Pecten varius. Janera, Schum.

  172.   ---- Plica. Decadopecten, Rüppell.

  173.   Hinnites Pusio. Pecten Pusio, Lam.

  174.   Lima squamosa.

  175.   Dianchora striata, (from Sow. Min. Con.)

  176.   Plagiostoma spinosum, (from Sow. Min. Con.)

  177.   Spondylus Americanus, hinge. (See Frontispiece.)

  178.   Plicatula gibbosa. Harpax, Parkinson.

  179.   Pedum Spondyloideum, (from Sow. Gen.)

         _Fam._ Ostracea.

  180.   Ostrea edulis.

  181.   ---- Folium. Dendostrea, Sw.

  182.   Gryphæa incurva.

  183.   Exogyra conica, (from Sow. Min. Con.)

  184.   Placuna placenta. _Gen._ Placenta, Schum.

  185.   Vulsella lingulata.

  186.   Anomia Ephippium.

  187.   Hinge of the same, with bony process.

  188.   Hinge, showing the fissure.

  189.   Placunanomia Cumingii.

  190.   Hinge of the same, showing the fissure.

  191.   Hinge of the unattached valve.

  192.   Mulleria. (from Sow. Gen.)

         _Fam._ Rudistis.

  193.   Sphærulites foliacea. (Radiolites is more conical.)

  194.   Calceola Sandalina.

  196.   Birostrites inæquiloba, internal cast of Sphærulites.

  197.   _a._ Crania personata, dorsal valve; _b._
           C. antiquata, interior.
         (This would be more properly placed in Brachiopoda.)

  198.   Hippurites Cornucopia, (from Blainville.)

  199.   Hipponyx Cornucopia, attached valve.

  200.   Upper valve of the same.

         _Fam._ Brachiopoda.

  201.   Orbicula lævis.

  202.   Terebratula Psittacea; _a._ anterior margin.

  203.   Atrypa reticularis. Trigonotreta, König.

  204.   Cyrtia exporrecta.

  205.   Delthyris plycotes, (from Dalman.)

  206.   Leptæna depressa, Dalman. Producta, Sow. (from Sow. Gen.)

  206*.  Producta antiquata.

  207.   Orthis basalis, Dalman. Strophomena, Rafinesque.

  208.   Trigonosemus Lyra, König.

  209.   Magas pumilus, Sow.

  210.   Gypidia conchidium, (from Dalman.)

  211.   Interior of the large valve of the same. (from Dalman.)

  212.   Pentamerus Aylesfordii, (from Sow. Min. Con.)

  213.   ---- lævis.

  214.   Spirifer trigonalis. }
                              } Trigonotreta, König, (from Sow. Gen.)
  215.   ---- dorsatus.       }

  216.   Thecidium recurvirostrum.
         (Here should come Crania, see Rudistes.)

  217.   Pycnodonta radiata, (from Fischer.)

  218.   Hinge of the same.

  219.   Lingula Anatina.

         _Class_, MOLLUSCA.
         _Order_, PTEROPODA.

  220.   Atlanta helicialis.

  221.   Cleodora cuspidata.

  222.   Creseis spinifera.

  223.   Cuvieria columella.

  224.   Spiratella limacinea, with animal; Limacella, Lam. Limacina
           Cuvier. (from Blainville.)

  225.   Vaginula Daudinii.

  226.   Hyalæa tridentata. Archonte, Montf.

         _Order_, GASTEROPODA.
         _Fam._ Phyllidiana.

  227.   Chiton spinosus.

  228.   Chitonellus striatus. (from Sow. Gen.)

  229.   Patella oculus; _a._ anterior.

  230.   Patella pellucida. Helcion, Montf. Ansates, Klein.

  231.   Patelloida Antillarum. Lottia, Gray.

  231*.  Siphonaria Sipho.

         _Fam._ Semiphyllidiana.

  232.   Pleurobranchus membranaceus.

  233.   Umbrella indica. Gastroplax, Bl.

         _Fam._ Calyptracea.

  234.   Calyptræe Equestris.

  235.   ---- extinctorium.

  236.   ---- auriculata.

  237.   ---- Pileus. Infundibulum, Montf.

  238.   Side view of the same.

  239.   Crepidula Porcellana.

  240.   Capulus ungaricus, two views. Pileopsis, Lam.

  241.   Emarginula fissura.

  242.   Parmophorus elongatus. Scutus, Montf.

  243.   Rimula Blainvillii.

  244.   Cemoria Flemingii.

  245.   Fissurella oriens.

  246.   Ancylus fluviatilis.

         _Fam._ Bullæana.

  247.   Bulla fragilis. Akera, Nonnul.

  248.   ---- aperta. Bullæa, Lam.

  249.   ---- aplustre. Aplustre, Schum.

  250.   ---- Naucum. Atys, Montf.

  251.   ---- lignaria. Scaphander, Montf.

  252.   ---- Ampulla.

  253.   ---- lineata.

         _Fam._ Aplysiacea.

  254.   Aplysia Petersoni.

  255.   Dolabella Rumphii.

         _Fam._ Limacinea.

  256.   Parmacella calyculata, Cryptella. Webb.

  257.   Parmacella Olivieri. (from De Ferussac.)

  258.   ---- palliolum. (from De Ferussac.)

  259.   Limax antiquorum.

  260.   Plectophorus corninus.

  261.   Testacella Haliotoidea.

  262.   Helixarion, Cuv.       }
                                }  Vitrina, Drap. Cobresia, Haubner.
  263.   Helicolimax pellucida. }

         _Order_, TRACHELIPODA.
         _Fam._ Colimacea.

                                                    _Sub-genera_ of De Fer.

  264.   Helix brevipes, Drap.                         Helicophanta.

  265.   Succinea amphibia.             }
                                        }              Cochlohydra.
  266.   ---- patula. Amphibulima, Lam. }

  267.   Helix hæmastoma. Acarus, }
                          Montf.  }
  268.   ---- Pomatia.            }                    Helicogena.
                                  }
  269.   Streptaxis contusa, Gray.}
                                  }
  270.   Another view of the same.}

  271.   Anastoma depressum.       }
                                   }
  272.   Another view of the same. }
                                   }
  273.   Helix nux-denticulata.    }                   Helicodonta.
                                   }
  274.   Proserpina nitida.        }
                                   }
  275.   Polygyra septemvolva.     }
                                   }
  276.   Another view of the same. }

  277.   Carocolla Lamarckii.          }
                                       }               Helicigona.
  278.   Helix pileus. Geotrochus, Sw. }

  279.   ---- algira. Zonites, Montf. }
                                      }                Helicella.
  280.   ---- citrina. Naninia, Gray. }

  281.   ---- epistilum      Helicostyla.

  282.   Bulinus rosaceus; _a._ apex. }
                                           }
  283.   ---- Guadaloupensis; Bulinulus,   }
                                Leach.     }           Cochlostyla.
  284.   ---- Lyonetianus. Gibbus, Montf.  }
                                           }
  285.   ---- lubricus. Cionella, Jeffreys.}

  286.   Achatina virginea Liguus, Montf. }
                                          }            Cochlitoma.
  287.   Achatinella, Sw.                 }

  288.   Polyphemus Glans, Montf.  Cochlicopa.

  289.   Bulinus decollatus, in a young state.         Cochlicella.

  290.   Azeca tridens, Jeffreys. Turbo tridens, }     Cochlogena.
                                         Gmelin. }

  291.   Pupa Uva.                  }
                                    }
  292.   Alæa marginata; Jeffreys.  }
                                    }                  Cochlodonta.
  293.   Vertigo pusilla.           }
                                    }
  294.   Megaspira Ruschenbergiana. }

  295.   Clausilia Macascarensis; _a_, a break, }
          to show the clausium.                      } Cochlodina.
                                                     }
  296.   Balea fragilis.                             }

  297.   Auricula Judæ.

  298.   ---- coniformis. Conovulum, Lam. Melampus, Montf.

  299.   Pedipes Adansonii.

  299*.  Scarabæus imbrium.

  300.   Chilina Dombeyana.

  301.   Carychium minimum.

  302.   Partula Australis.

  303.   Cyclostoma ferrugineum.

  304.   ---- Involvulus. Cyclophorus, Montf.

  305.   Nematura Deltæ.

  306.   Helicina major.

  307.   Operculum of the same.

         _Fam._ Lymneana.

  308.   Limnæa stagnalis.

  309.   ---- auricularia. Radix, Montf.

  310.   ---- castanea. Physa, Drap.

  311.   Planorbis corneus.

  312.   Planaria niteus, (from Lea.)

         _Fam._ Melaniana.

  313.   Melania subulata. Melas, Montf.

  314.   Melania prærosa and monodontoides. Anculosa, Say.

  315.   Melanopsis costata. Faunus, Montf.

  316.   Pirena terebralis.

  317.   Pasithæa striata, (from Lea.)

         _Fam._ Peristomata.

  318.   Ampullaria fasciata. Amphibola; _a_, aperture.

  319.   ---- Guinaica. Lanistes, Montf.

  320.   ---- Cornu-arietis. Ceradotes, Guild.

  321.   Paludina Bengalensis.

  322.   Valvata piscinalis.

         _Fam._ Neritacea.

  323.   Navicella elliptica.

  324.   Neritina virginea. Theodoxus, Montf.

  325.   ---- spinosa. Clithon, Montf.

  326.   ---- perversa. Velates, Montf. (from Sow. Gen.)

  327.   Natica mamilla. Polinices, Montf.

  328.   ---- lineata.

  330.   Nerita peloronta. Peloronta, Oken.

  331.   Neritopsis granosa.

  332.   Pileolus plicatus.

  333.   Janthina fragilis.

         _Fam._ Macrostomata.

  334.   Sigaretus concavus.

  335.   Stomatia Phymotis.

  336.   Stomatella imbricata.

  337.   Velutina lævigata. Galericulus, Nonnul.

  338.   Haliotis rubra, young.

  339.   ---- tricostalis, Lam. Padollus, Montf.

  340.   Scissurella elatior, magnified. }
                                         }      (from Sow. Gen.)
  341.   Pleurotomaria reticulata.       }

         _Fam._ Plicacea.

  342.   Pyramidella terebellum.

  343.   Tornatella solidula. Acteon, Montf.

  344.   Monoptygma elegans. (from Lea.)

         _Fam._ Scalariana.

  345.   Vermetus lumbricalis.

  346.   Rissoa reticulata.

  347.   Eulima labiosa.

  348.   ---- marmorata. Bonellia, Desh.

  349.   Cirrus nodosus, Sow.

  350.   Euomphalus pentangulus. (from Sow. Min. Con.)

  351.   Scalaria Pallassii. Aciona, Leach.

  352.   Delphinula laciniata.

         _Fam._ Turbinacea.

  353.   Solarium perspectivum.

  354.   ---- Bifrons. Bifrontia and Omalaxis, Desh.

  355.   Orbis Rotella. (from Lea.)

  356.   Another view of the same.

  357.   Rotella vestiaria, Pitonellus, Montf.

  358.   Trochus stellaris, Lam. Calcar, Montf. Turbo, Sow.

  359.   ---- maculatus. Tectus, Montf.

  360.   ---- agglutinans. Phorus.

  361.   ---- Pharaonis. Clauculus, Montf.

  362.   Margarita tæniata.

  363.   Littorina vulgaris.

  363*.  Assiminea Grayana.

  364.   Lacuna pallidula.

  365.   Planaxis sulcata.

  366.   Monodonta labeo; Odontis, Sow.

  367.   Phasianella variegata.

  368.   Turbo setosus. Marmarostoma, Sw.

  369.   Tuba striata. (from Lea.)

  370.   Turritella imbricata.

  371.   Monotygma, Gray.

         _Fam._ Canalifera.

  372.   Cerithium Aluco, front.

  374.   Nerinea Goodhallii. (from Geol. Trans.)

  375.   Triphora plicata. (from Deshayes.)

  376.   End view of the same.

  377.   Potamis muricata. Pyrazus, Montf. Tympanostomata, Schum.

  378.   Cerithium Telescopium. _Gen._ Telescopium.

  379.   Pleurotoma Babylonia; _a, a_, extremities of the axis.

  381.   ---- strombiformis, Clavatula, Lam.

  382.   Turbinella corniger. Scolymis, Sw.

  383.   ---- polygona. Polygonum, Schum.

  384.   Spirillus. _Gen._ Pyrella, Sw. Turbinella spirillus, Auct.

  385.   Cancellaria reticulata.

  386.   Fasciolaria Trapezium.

  387.   Fusus Colus; _a_, anterior of the aperture; p, posterior.

  388.   Pyrula perversa. Fulgur, Montf.

  389.   ---- papyracea. Rapanus, Schum. Bulbus, Humph. Rapella, Sw.

  390.   ---- Ficus. Ficula, Sw.

  391.   Struthiolaria straminea.

  393.   Ranella ranina. Apollon, Montf.

  394.   ---- neglecta. Bufo, Montf.

  395.   Murex inflatus. Chicoreus, Montf.

  396.   ---- haustellum. Brontes, Montf.

  397.   Typhis tubifer. (from Deshayes.)

  398.   Triton pilearis.

  399.   ---- cutaceus. Aquillus, Montf.

  400.   ---- Lotorium. Lotorium, Montf.

  401.   ---- anus. Persona, Montf.

         _Fam._ Alatæ.

  402.   Rostellaria curvirostrum.

  403.   ---- columbaria. Hippochrenes, Montf. (from Sow. Gen.)

  404.   ---- Pes-pelicani. Aporrhais, Petiver.

  405.   Pteroceras aurantiacum.

  406.   Strombus pugilis.

         _Fam._ Purpurifera.

  407.   Cassidaria echinophora. Morio, Montf.

  408.   Side view of the outer lip, to shew the canal.

  409.   Oniscia Oniscus. Cassidara.

  410.   Cassis tuberosa, reduced.

  411.   ---- erinaceus. Cassidea, Sw.

  412.   ---- testiculus. Cypræcassis, Stutchbury.

  413.   Ricinula horrida. Sistrum, Montf.

  414.   Purpura persica.

  415.   Tritonidea (_Pollia_, Gray.) articularis.

  416.   Phos senticosa.

  417.   Monoceros crassilabrum.

  418.   Concholepas Peruviana.

  419.   Harpa ventricosa.

  420.   Dolium maculatum.

  421.   Buccinum undatum; _a_, anterior of the aperture; _p_, posterior.

  422.   ---- papillosum. Alectrion, Montf.

  423.   Nassa arcularia.

  424.   ---- neritoidea. Cyclops, Montf.

  425.   Cyllene, Gray.

  426.   Eburna Zeylanica.

  427.   Bullia vittata.

  428.   Terebra maculata. Subula, Bl.

  429.   Trichotropis bicarinata.

         _Fam._ Columellata.

  430.   Columbella mercatoria.

  431.   Mitra plicaria; _c_, termination of the columella.

  432.   Conohelix marmorata.

  433.   Voluta Vespertilio. Cymbiola, Sw.

  434.   Cymba porcina.

  435.   Melo Æthiopicus.

  436.   Volutilithes spinosus.

  437.   Marginella Glabella. Glabella, Sw. Cucumis, Klein.

  438.   ---- persicula. Volutella, Sw. Persicula, Schum.

  439.   Volvaria concinna.

         _Fam._ Convolutæ.

  440.   Ovulum Ovum.

  441.   ---- verrucosum. Calpurnus, Montf.

  442.   ---- Volva. Radius, Montf.

  443.   ---- gibbosum. Ultimus, Montf.

  444.   Cypræovulum capense.

  445.   Cypræa arabica, back.

  446.   The same, front.

  447.   Cypræa Algoensis. Luponia, Gray, front.

  449.   ---- Pediculus. Trivia, Gray, back.

  450.   The same, front.

  451.   Terebellum convolutum. Seraphs, Montf.

  452.   ---- subulatum, front.

  454.   Erato Mangeriæ.

  455.   Ancillaria glabrata. Anolax, Brongn.

  456.   ---- cinnamonea.

  457.   Oliva Maura.

  458.   ---- subulata. Hiatula, Sw.

  459.   Conus nocturnus. Rhombus, Montf.

  460.   ---- Nussatella. Hermes, Montf.

  461.   ---- Textile. Cylinder, Montf.

  462.   ---- geographus. Rollus, Montf.

         _Order._ CEPHALOPODA.
         _First Division._ Polythalamous Cephalopoda.
         _Fam._ Orthocerata.

  463.   Amplexus coralloides. (from Sow. Min. Con.)

  464.   Orthoceratites annulatus.

  465.   Nodosaria æqualis.

  466.   Belemnites, with the outer coat broken to shew the alveole.

  467.   ---- portion of the alveole separated.

  468.   ---- hastatus. Hibolithes, Montf. (from Blainville.)

  469.   Conularia quadrisulcata.

  470.   Conilites pyramidatus, (from Blainville.)

         _Fam._ Lituacea.

  471.   Spirula Peronii.

         _Fam._ Nautilacea.

  472.   Nummulites buticularis, outside. Helicites, Bl. Camerina, Brookes.

  473.   The same inside, to shew the chambers.

  474.   Nautilus pompilius, young. See Frontispiece.

  475.   Simplegas sulcata.

  476.   Endosiphonites. (from Camb. Philos. Trans.)

         _Fam._ Ammonacea.

  477.   Ammonoceras. (from Blainville.)

  478.   Ammonites; _a_, break in the shell, showing the sinuous septa.

  479.   Orbulites crassus. Globulites, Nonnul. Angulites, Montf. reduced.

  479*.  ---- discus. Aganides, Montf.

  480.   Goniatites striatus.

  481.   Scaphites æqualis.

  482.   Crioceratites Duvallii.

  483.   Turrilites tuberculatus.

  484.   Baculites Faujasii. Portion near the centre.

  484*.  Hamites cylindricus; _a_, internal cast of part of the shell;
           _b_, hollow external cast of the remainder.

         _Second Division._ Monothalamous Cephalopoda.

  485.   Argonauta Argo.

  486.   Bellerophon tenuifasciata. (from Sow. Gen.)

  487.   The same, shewing the dorsal keel.

         _Order._ HETEROPODA.

  488.   Carinaria Mediterranea.

       *       *       *       *       *

EXPLANATION OF THE NEW PLATES.

         _Order._ SESSILE CIRRIPEDES.

  489.   Pyrgoma monticularia. _Sub-genus_, Daracia, Gray, back and
           front.

  490.   The same, in situ.

         _Fam._ Myaria.

  491.   Lyonsia Norvegica. Anatina, Nonnul. Inside view of both valves.

  492.   Outside, with the valves closed.

  493.   Næra longirostrum. Anatina longirostris, Lam. Inside of both
           valves.

  494.   Outside, with both valves closed.

  495.   A smaller species of Næra, shewing the inequality of the valves.

         _Fam._ Mactracea.

  496.   Amphidesma tennis. Abra, Leach.

  497.   Ervillia nitens.

         _Fam._ Corbulacea.

  498.   Potamomya, of some authors. A fresh-water shell resembling
           Corbula. Outside, valves closed.

  499.   Inside of both valves.

         Fluviatile Conchacea.

  500.   Cyclas amnica. Pera, Leach.

         _Fam._ Cardiacea.

  501.   Cardilia semisulcata. Isocardia semisulcata, Lam. Internal view.

  502.   External view of the same valve.

  503.   Cardium apertum. Papyridea, Sw.

  504.   The same, shewing the umbones.

  505.   Pleurorynchus, fossil, (from Mineral Conchology.)

         _Fam._ Phyllidiana.

  506.   Chiton fascicularis. Phakellopleura, Guild.

  507.   ---- amiculatus. Amicula, Gray.

         _Fam._ Calyptracea.

  508.   Scutella, Brod. Internal view.

  509.   External view of the same.

  510.   Ancylus, a reversed species, illustrating the genus Velletia,
           Gray. Enlarged view.

  511.   The same, natural size.

  512.   Pedicularia. Enlarged figure, (copied from Swainson.)

  513.   The same, natural size, growing on coral.

         _Fam._ Colimacea.

  514.   Achatina? octona. Macrospira, Guild.

  515.   Stenopus cruentatus, Guild. Under side.

  516.   ---- lividus.

  517.   Helix, the aperture covered by the epiphragm.

  518.   Pupa secale, Drap. Abida, Leach.

  519.   ---- pagoda. Gonidomus, Sw.

  520.   Truncatella, enlarged figure.

  521.   The same, natural size.

  522.   Auricula caprella. _Gen._ Caprella, Nonnul. Front view.

  523.   The same, dorsal view.

  524.   Pupina vitrea.

  526.   ---- antiquata.

  527.   ---- Namezii.

  528.   ---- lubrica. Callia? Gray.

  529.   Cyclostoma, a pupiform species. Megalomastoma, Guild.

  530.   ---- Planorbulum. Cyclotus, Guild.

  531.   ---- a similar species, with the complicated notch at the
           posterior part of the aperture. Pterocyclos, Gray.

  532.   Helicina acutissima, nobis. View of the under side. Trochatella,
           Sw.

  533.   The same in profile.

  534.   }
         }
  535.   } Strophostoma, Desh. three views.
         }
  536.   }

         _Fam._ Peristomata.

  537.   Paludina impura. Bithinia, Gray?

  538.   Ampullaria avellana. Thallicera, Sw. Ampullarina?

  539.   A species of Ampullaria having a thickened ledge on which the
           shelly operculum rests. Pachystoma, Guild. changed to
           Pachylabra, Sw.

         _Fam._ Plicacea.

  540.   Ringicula, Desh. A fossil species, front view.

  541.   Back view of the same.

         _Fam._ Turbinacea.

  542.   Turbo nicobaricus. Chrysostoma, Sw.

  543.   Trochus Iris. Elenchus, Humph.

         _Fam._ Purpurifera.

  544.   Purpura vexilla. _Gen._ Vexilla, Sw.

  545.   Priamus. Achatina priamus, Auct. The propriety of placing it in
           this family will depend upon the correctness of the statement
           made by Dr. Beck that this shell is marine, and possesses an
           operculum.

  546.   Purpura crispata. Polytropa, Sw.

  547.   Pseudoliva plumbea. Gastridium, Sow.

         _Fam._ Canalifera.

  548.   Fusus longevus. Clavalithes, Sw.

  549.   ---- bulbiformis. Leiostoma, Sw.

  550.   Pyrella, Sw. Turbinella Spirillus, Auct.

  551.   Pleurotoma lineata. Tomella, Sw.

  552.   Pyrula melongena. _Gen._ Myristica, Sw.

  553.   Murex vitulinus. _Gen._ Vitulina, Sw.

  554.   Typhis Sowerbii.

  555.   A brown variety of the same.

  556.   Typhis Cumingii.

         _Fam._ Columellata.

  557.   Voluta Vexillum. Harpula, Sw.

  558.   Mitra monodonta. Mitreola, Sw.

  559.   ---- bicolor. Mitrella, Sw.

  560.   Columbella nitidella. _Gen._ Nitidella, Sw.

         _Fam._ Convolutæ.

  561.   Oliva volutella. _Gen._ Lamprodoma, Sw.

  562.   ---- maura.

  563.   Cypræa Globulus. _Gen._ Globularia, Sw.

  564.   ---- pulchella, fossil. _Gen._ Cyprædia, Sw.

THE END.

       *       *       *       *       *


TABLE OF LAMARCK'S CONCHOLOGICAL SYSTEM.

  _Classes of
  Invertebrated  _Orders._  _Families._        _Genera._
    Animals._

  ANNELIDES.  Sedentary     _Dorsalia_         Siliquaria.
                            _Maldania_         Dentalium.
                            _Serpulacea_       Serpula, Spirorbis,
                                               Galeolaria, Vermilia,
                                               Magilus.

  CIRRIPEDES. Sessile                          Tubicinella, Coronula,
  _Multivalve._                                Balanus, Acasta, Pyrgoma,
                                               Creusia.

              Pedunculated                     Anatifer, Pollicipes,
                                               Cineras, Otion.

  CONCHIFERA  Dimyaria      _Tubicolaria_      Aspergillum, Clavagella,
  _Bivalve._                                   Fistulana, Septaria, Teredo,
                                               Teredina.
                            _Pholadaria_       Pholas, Gastrochæna.
                            _Solenacea_        Solen, Panopæa, Glycimeris.
                            _Myaria_           Mya, Anatina.
                            _Mactracea_        Lutraria, Mactra,
                                               Crassatella, Erycina,
                                               Ungulina, Solemya,
                                               Amphidesma.
                            _Corbulacea_       Corbula, Pandora.
                            _Lithophagidæ_     Saxicava, Petricola,
                                               Venerirupis.
                            _Nymphacea_        Sanguinolaria, Psammobia,
                                               Psammotæa, Tellina,
                                               Tellinides, Corbis, Lucina,
                                               Donax, Capsa, Crassina.
                            _Fluviatile        Cyclas, Cyrena, Galathæa.
                              Conchacea_
                            _Marine Conchacea_ Cyprina, Cytheræa, Venus,
                                               Venericardia.
                            _Cardiacea_        Cardium, Cardita,
                                               Cypricardia, Hiatella,
                                               Isocardia.
                            _Arcacea_          Cucullæa, Arca,
                                               Pectunculus, Nucula.
                            _Trigonacea_       Trigonia, Castalia.
                            _Nayades_          Unio, Hyria, Anodon,
                                               Iridina.
                            _Chamacea_         Diceras, Chama, Etheria.

              Monomyaria    _Tridacnacea_      Tridacna, Hippopus.
                            _Mytilacea_        Modiola, Mytilus, Pinna.
                            _Malleacea_        Crenatula, Perna, Malleus,
                                               Avicula, Meleagrina.
                            _Pectenides_       Pedum, Lima, Plagiostoma,
                                               Pecten, Plicatula,
                                               Spondylus, Podopsis.
                            _Ostracea_         Gryphæa, Ostræa, Vulsella,
                                               Placuna, Anomia.
                            _Rudistes_         Sphærulites, Radiolites,
                                               Calceola, Birostrites,
                                               Discina, Crania.
                            _Brachiopoda_      Orbicula, Terebratula,
                                               Lingula.

  MOLLUSCA    Pteropoda                        Hyalæa, Cleodora, Limacina,
  _Univalve._                                  Cymbulia.

              Gasteropoda   _Phyllidiana_      Chiton, Chitonellus,
                                               Patella.
                            _Semiphyllidiana_  Pleurobranchus, Umbrella.
                            _Calyptracea_      Parmophorus, Emarginula,
                                               Siphonaria, Fissurella,
                                               Pileopsis, Calyptræa,
                                               Crepidula, Ancylus.
                            _Bulleana_         Bulla, Bullæa.
                            _Aplysiacea_       Aplysia, Dolabella.
                            _Limacinea_        Parmacella, Limax,
                                               Testacella, Vitrina.

              Trachellipoda _Colimacea_        Helix, Carocolla, Anastoma,
                                               Helicina, Pupa, Clausilia,
                                               Bulinus, Achatina, Succinea,
                                               Auricula, Cyclostoma.
                            _Lymneana_         Planorbis, Physa, Lymnæa.
                            _Melaniana_        Melania, Melanopsis, Pirena.
                            _Peristomata_      Valvata, Paludina,
                                               Ampullaria.
                            _Neritacea_        Navicella, Neritina, Nerita,
                                               Natica, Janthina.
                            _Macrostomata_     Stomatia, Stomatella,
                                               Haliotis.
                            _Plicacea_         Tornatella, Pyramidella.
                            _Scalariana_       Vermetus, Scalaria,
                                               Delphinula.
                            _Turbinacea_       Solarium, Rotella, Trochus,
                                               Monodonta, Turbo, Planaxis,
                                               Phasianella, Turitella.
                            _Canalifera_       Cerithium, Pleurotoma,
                                               Turbinella, Cancellaria,
                                               Fasciolaria, Fusus, Pyrula,
                                               Ranella, Murex, Triton.
                            _Alata_            Rostellaria, Strombus,
                                               Pteroceras.
                            _Purpurifera_      Cassidaria, Cassis,
                                               Ricinula, Purpura,
                                               Monoceros, Concholepas,
                                               Harpa, Dolium, Buccinum,
                                               Eburna, Terebra.
                            _Columellata_      Columbella, Mitra, Voluta,
                                               Marginella, Volvaria.
                            _Convoluta_        Ovulum, Cypræa, Oliva,
                                               Ancillaria, Conus.

              Polythalamous _Orthocerata_      Belemnites, Orthoceras,
                Cephalopoda                    Nodosaria, Hippurites,
                                               Conilites.
                            _Lituacea_         Spirula, Spirolina, Lituola.
                            _Cristacea_        Renulina, Cristellaria,
                                               Orbiculina.
                            _Spherulacea_      Miliola, Gyrogona, Melonia,
                                               (Microscopic.)
                            _Radiolacea_       Rotalites, Lenticulina,
                                               Placentula, (Micros.)
                            _Nautilacea_       Discorbites, Siderolites,
                                               Polystomella, Vorticialis,
                                               Nummilites, Nautilus.
                            _Ammonacea_        Ammonites, Ammonoceras,
                                               Turrilites, Baculites.

              Monothalamous                    Argonauta.
                Cephalopoda

              Heteropoda                       Carinaria.

       *       *       *       *       *

TABLE OF THE CONCHOLOGICAL SYSTEM OF DE BLAINVILLE.

  Key.
  1 = TYPE MALACOZOARIA
  2 = SUB-TYPE MALENTOZOARIA

  CLASSES
  A = CEPHALOPHORA
  B = PARACEPHOLOPHORA DIOICA
  C = PARACEPHALOPHORA MONOICA
  D = PARACEPHALOPHORA HERMAPHRODITA
  E = ACEPHALOPHORA
  F = NEMATOPODA
  G = POLYPLAXIPHORA

  ORDERS
  a = Cellulacea
  b = Polyphalamacea
  c = Siphonobranchiata
  d = Asiphonibranchiata
  e = Pulmobranchiata
  f = Chismobranchiata
  g = Monopleurobranchiata
  h = Aporobranchiata
  i = Nucleobranchiata
  j = Cirrobranchiata
  k = Cervicobranchiata
  l = Scutibranchiata
  m = Palliobranchiata
  n = Rudistes
  o = Lamellibranchiata

           _Classes._     _Families._        _Genera._
                  _Orders._

                         {_Planulacea_       Renulina, Peneroplis.
                         {
                     { a {_Sphærulacea_     {Miliola, Pollontes, Melonia,
                     {   {                  {Saracenaria, Textularia.
                     {   {
                     {   {_Nummulacea_      {Nummulites, Orbiculina,
                     {                      {Helicites, Placentula,
                     {                      {Vorticialis, Siderolites.
                 { A {
                 {   {   {_Orthocerata_     {Belemnites, Conularia,
                 {   {   {                  {Conilites, Orthoceras,
                 {   {   {                  {Baculites.
                 {   {   {
                 {   {   {_Lituacea_        {Icthysarcolites, Lituola,
                 {   {   {                  {Spirula, Spirolina,
                 {   {   {                  {Hamites, Ammonoceras.
                 {   {   {
                 {   { b {_Cristacea_        Crepidulina, Oreas, Linthuris.
                 {       {
                 {       {_Ammonacea_       {Discorbis, Scaphites,
                 {       {                  {Ammonites, Simplegas.
                 {       {
                 {       {_Nautilacea_      {Polystomelle, Nautilus,
                 {       {                  {Lenticulina.
                 {       {
                 {       {_Turbinacea_       Cibicides, Rotalia.
                 {       {
                 {       {_Turriculacea_     Turrilites.
                 {
                 {                          {Pleurotoma, Rostellaria,
                 {                          {Fusus, Pyrula,
                 {       {_Siphonostomata_  {Fasciolaria, Turbinella,
                 {       {                  {Columbella, Triton,
                 {       {                  {Struthiolaria, Ranella,
                 {       {                  {Murex.
                 {       {
                 {       {                  {Cerithium, Pyrena, Melanopsis,
                 {       {                  {Planaxis, Subula, Terebra,
                 {       {                  {Eburna, Buccinum, Harpa,
                 {   { c {_Entomostomata_   {Dolium, Cassis, Cassidaria,
                 {   {   {                  {Ricinula, Cancellaria,
                 {   {   {                  {Purpura, Concholepas, Terebra,
                 {   {   {                  {Mitra
                 {   {   {
    {_Univalves_ {   {   {                  {Strombus, Conus, Terebellum,
    {            {   {   {_Angyostomata_    {Oliva, Ancillaria, Voluta,
    {            {   {                      {Mitra, Marginella, Volvaria,
    {            {   {                      {Cypræa, Ovulum.
    {            {   {
    {            {   {   {_Goniostomata_     Solarium, Trochus.
    {            { B {   {
    {            {   {   {                  {Monodonta, Turbo,
    {            {   {   {                  {Pleurotomaria, Littorina,
    {            {   {   {                  {Delphinula, Cyclostoma,
    {            {   {   {_Cricostomata_    {Paludina, Valvata, Scalaria,
    {            {   {   {                  {Proto, Turitella, Vermetus,
    {            {   {   {                  {Siliquaria, Magilus.
    {            {   {   {
    {            {   { d {_Hemicyclostomata_{Nerita, Neritina, Clithon,
    {            {       {                  {Velates, Pileolus, Navicella,
    {            {       {                  {Natica.
    {            {       {
    {            {       {_Ellipsostomata_  {Helicina, Ampullaria, Melania,
    {            {       {                  {Rissoa, Phasianella,
    {            {       {                  {Pleurocerus.
    {            {       {
    {            {       {_Oxystomata_       Janthina.
    {            {
    {            {       {_Limnacea_         Limnæa, Physa, Planorbis.
    {            {       {
    {            {       {_Auriculacea_     {Auricula, Pedipes, Tornatella,
    {            { C   e {                  {Tomogerus, Pyramidella.
    {            {       {
    {            {       {                  {Succinea, Bulinus, Achatina,
    {            {       { _Limacinea_      {Clausilia, Pupa, Partula,
    {            {                          {Helix, Vitrina, Testacella,
    {            {                          {Parmacella, Limacella, Limax.
    {            {
    {            {     f                    {Sigaretus, Cryptostomata,
    {            {                          {Stomatella, Velutina.
    {            {
  1 {            {       {_Sub-aplysiaca_    Pleurobranchus.
    {            {       {
    {            {     g {_Aplysiaca_        Aplysia, Dolabella.
    {            {       {
    {            {       {_Patelloidea_      Umbrella, Siphonaria.
    {            {       {
    {            {       {_Akera_            Bulla, Bellerophon, Sormetus.
    {            {
    {            {     h  _Thecosomata_      Hyalæa, Cleodora, Cymbulia.
    {            {
    {            {       {_Nectopoda_        Carinaria.
    {            {     i {
    {            {       {_Pteropoda_       {Atlanta, Spiratella,
    {            {                          {Argonauta.
    {            {
    {            {   { j                     Dentalium.
    {            {   {
    {            {   {   {_Retifera_         Patella.
    {            { D { k {
    {                {   {_Branchifera_     {Fissurella, Emarginula,
    {                {                      {Parmophorus.
    {                {
    {                {   {_Otides_           Haliotis, Ancylus.
    {                { l {
    {                    {_Calyptracea_     {Crepidula, Calyptræa,
    {                                       {Capulus, Hipponyx, Notrema.
    {
    {                                        {Lingula, Terebratula,
    {                {                       {Strophomena, Dianchora,
    {                { m                     {Thecidium, Plagiostoma,
    {                {                       {Podopsis, Orbicula, Crania.
    {                {
    {                { n                     {Sphærulites, Hippurites,
    {                {                       {Radiolites, Birostrites,
    {                {                       {Calceola.
    {_Bivalves_    E {
                     {   {_Ostracea_         {Anomia, Placuna, Ostræa,
                     {   {                   {Gryphæ.
                     {   {
                     {   {_Sub-ostracea_     {Spondylus, Plicatula,,
                     {   {                   {Hinnites, Pecten, Pedum,,
                     {   {                   {Lima.
                     {   {
                     {   {                   {Vulsella, Malleus, Avicula,
                     {   {_Margaritacea_     {Perna, Crenatula, Inoceramus,
                     {   {                   {Catillus, Pulvinites,
                     {   {                   {Gervillia.
                     {   {
                     {   {_Mytilacea_         Pinna, Mytilus.
                     {   {
                     {   {_Arcacea_           Arca, Pectunculus, Nucula.
                     {   {
                     {   {_Sub-mytilacea_     Anodon, Unio, Cardita.
                     {   {
                     {   {_Chamacea_         {Chama, Diceras, Etheria,
                     {   {                   {Tridacna, Hippopus,
                     {   {                   {Isocardium, Trigonia.
                     {   {
                     { o {                   {Cardium, Donax, Tellina,
                         {                   {Lucina, Cyclas, Cyprina,
                         {_Conchacea_        {Mactra, Erycina, Crassatella,
                         {                   {Venerirupis, Venus,
                         {                   {Coralliophaga, Clotho,
                         {                   {Corbula, Sphænia, Ungulina.
                         {
                         {                   {Pandora, Anatina, Thracia,
                         {                   {Mya, Lutricola, Psammocola,
                         {                   {Soletellina, Sanguinolaria,
                         {_Pylorides_        {Solenocurtus, Solen, Solemya,
                         {                   {Panopæa, Glycimeris,
                         {                   {Saxicava, Byssomya,
                         {                   {Rhomboides, Gastrochæna,
                         {                   {Clavagella, Aspergillum
                         {
                         {_Adesmacea_        {Pholas, Teredina, Teredo,
                                             {Fristulana, Septaria.

                         {_Lepadicea_        {Gymnolepas, Pentalepas,
                         {                   {Polylepas, Litholepas.
                 { F     {
                 {       {_Balanidea_        {Balanus, Acasta, Octhosia,
  2 _Multivalves_{                           {Conia, Creusia, Pyrgoma,
                 {                           {Chthalamis, Coronula,
                 {                           {Chelnobia, Cetopirus,
                 {                           {Diadema, Tubicinella.
                 {
                 { G      _Seriales_         {Chiton, Chitonellus.

[Illustration: Fig. 1 to 33.]

[Illustration: Fig. 34 to 59.]

[Illustration: Fig. 60 to 78.]

[Illustration: Fig. 79 to 100.]

[Illustration: Fig. 101 to 116.]

[Illustration: Fig. 117 to 126 and 128.]

[Illustration: Fig. 127 and 129 to 141.]

[Illustration: Fig. 142 to 152.]

[Illustration: Fig. 153 to 166. 165 next plate.]

[Illustration: Fig. 165. 167 to 182.]

[Illustration: Fig. 183 to 213. 195. cancelled.]

[Illustration: Fig. 214 to 242.]

[Illustration: Fig. 243 to 278.]

[Illustration: Fig. 279 to 317.]

[Illustration: Fig. 318 to 348.]

[Illustration: Fig. 349 to 381. 377. 378. in the next.]

[Illustration: Fig. 377. 378. 382 to 397. 383 in the next.]

[Illustration: Fig. 383. 398 to 406. 409.]

[Illustration: Fig. 407 to 425. 409 in the last.]

[Illustration: Fig. 426 to 443.]

[Illustration: Fig. 444 to 462.]

[Illustration: Fig. 463 to 479.]

[Illustration: Fig. 479* to 488.]

[Illustration: Fig. 489 to 513.]

[Illustration: Fig. 514 to 545.]

[Illustration: Fig. 546 to 564.]

       *       *       *       *       *


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bd. morocco_, 2l 2s

1838

    "Admirable figures, full of truth and nature; accompanied by valuable
    observations on the habits and economy of the birds."--_Swainson._

    "According to the first ornithologists of the day, these plates are of
    permanent value."--_Wood._

LINDLEY'S BRITISH FRUITS; or Figures and Descriptions of the most Important
Varieties of Fruit Cultivated in Great Britain, 3 vols. royal 8vo.
_containing 152 most beautifully coloured plates, chiefly by Mrs. Withers,
Artist to the Horticultural Society_, (published at 10l 10s) _elegantly hf.
bd. green morocco extra, gilt edges_, 5l 5s

1841

    This is an exquisitely beautiful work. Every plate is like a highly
    finished drawing, similar to those in the Horticultural Transactions.

LINDLEY'S LADIES' BOTANY; or a Familiar Introduction to the Study of the
Natural System of Botany, _new edition_, 12mo. _with numerous wood-cuts_,
(published at 12s) _elegantly bound in cloth, with gilt back and sides_, 7s

1841

---- the same, _with the plates coloured, extra gilt cloth_, 12s

    "The want of a popular Introduction to the study of Botany on the
    improved natural system has been completely removed by this volume of
    Dr. Lindley's. It is accurate in its science, graceful in its style,
    and familiar in its language; it enables the student to take some
    common, or easily accessible plant, as the representative of each
    natural family, to examine its several parts, to compare them with the
    plates, and learn their uses from the descriptions; when he has done
    this with care, and understood, and remembered what he has done, he
    will be a Botanist; if not a learned one, at least acquainted with all
    the fundamental facts of the science."

    _Athenæum._

    "We are infinitely indebted to Professor Lindley for leading us so far
    in the study of Botany in a plain and intelligible way. A multitude of
    plates, a clear text, and a most judicious and agreeable arrangement,
    render this introduction to perhaps the most innocent and delightful of
    all studies, truly acceptable."

    _Literary Gazette._

MANTELL'S FOSSILS OF THE SOUTH DOWNS, or ILLUSTRATIONS of the GEOLOGY of
SUSSEX, royal 4to. _with 42 plates_, (published at 3l 3s) _extra cloth
bds_. 2l 2s

1822

    "My attention was first drawn to these remains by Mr. Mantell, who has
    illustrated the subject in his excellent work on the Fossils of the
    South Downs."

    _Parkinson's Organic Remains._

    "For the detailed history of the Organic Remains of the Wealden
    formation, see Mr. Mantell's highly instructive and accurate volume on
    the Geology of Sussex."

    _Buckland's Bridgewater Treatise._

MARTIN'S (P. I.) GEOLOGICAL MEMOIR ON A PART OF WESTERN SUSSEX, with some
Observations upon Chalk-Basins, the Weald-Denudation, and
Outliers-by-Protrusion, 4to. _large map and coloured plates_, (published at
1l) _cloth bds._ 12s

1828

MUDIE'S (ROBT.) HISTORY OF BRITISH BIRDS, or the Feathered Tribes of the
British Islands, 2 vols. 8vo. _second edition, the plates beautifully
coloured_, (published at 1l 8s) _extra cloth bds. elegantly gilt on the
backs_, 16s

1835

    "This is, without any exception, the most truly charming work on
    Ornithology which has hitherto appeared, from the days of Willughby
    downwards. Other authors describe, Mudie paints; other authors give the
    husk, Mudie the kernel. We most heartily concur with the opinion
    expressed of this work by Leigh Hunt (a kindred spirit) in the first
    few numbers of his right pleasant _London Journal_. The descriptions of
    Bewick, Pennant, Lewin, Montagu, and even Wilson, will not for an
    instant stand comparison with the spirit-stirring emanations of Mudie's
    'living pen,' as it has well been called. We are not acquainted with
    any author who so felicitously unites beauty of style with strength and
    nerve of expression--he does not specify, he paints."

    _Wood's Ornithological Guide._

    "The '_Feathered Tribes_' is indeed an EXQUISITE WORK, and
    unquestionably the best that has yet appeared on the habits of our
    native birds, in that it is scarcely second to those of Wilson and
    Audubon. Mudie is the most accurate observer of nature,--Selby
    excepted, and he treats not exclusively of habits--consequently the
    '_Feathered Tribes_' deserves a distinguished place on the shelves of
    the philosophic ornithologist."--_Ornithologist's Text Book._

PARKINSON'S ORGANIC REMAINS OF A FORMER WORLD, being an Examination of the
Mineralized Remains of the Vegetables and Animals of the Antediluvian
World, generally termed Extraneous Fossils, 3 vols. 4to. _with 54 coloured
plates by Sowerby, exhibiting above 700 Fossil Remains_, (published at 10l
10s) _extra cloth bds._ 4l 4s

    This distinguished work is continually referred to by Dr. Buckland in
    his Bridgewater Treatise.

    "A work on the same subject, equally elegant, comprehensive, and
    impartial, does not exist in English; nor, as far as we know, in any
    other language. It is written in a plain, intelligible, and equal
    style, such as may, with pleasure, be perused by all classes of
    readers."--_British Critic._

    "'Organic Remains of a Former World,' replete with interest and
    instruction."--_Dr. Mantell._

PARKINSON'S INTRODUCTION TO THE STUDY OF FOSSIL ORGANIC REMAINS; especially
those found in the British Strata, intended to aid the Student in his
Inquiries respecting the Nature of Fossils, and their Connection with the
Formation of the Earth, 3rd edition, 8vo. _illustrated by 220 Fossil
Specimens_, (published at 12s) _extra cloth bds._ 8s

    "In this well-printed volume, which may be called a grammar of
    Oryctology, Mr. Parkinson has comprised an extensive and well-arranged
    variety of information on the subject of fossil organic remains;
    supplying to the learner, an easy and complete introductory manual; and
    to the well-informed, a text-book of convenient reference. The graphic
    illustrations are copious and distinct."--_Eclectic Review._

PURSH'S FLORA AMERICÆ SEPTENTRIONALIS; or a Systematic Arrangement and
Description of the Plants of North America; containing, besides what have
been described by preceding Authors, many new and rare species, collected
during twelve years travels and residence in that country, 2 vols. 8vo.
_with 24 plates_, (published at 1l 16s) _cloth_, 14s

---- the same, _with the plates beautifully coloured_, (published at 2l 12s
6d) _cloth_, 1l 1s

1814

RICHARDSON'S FAUNA BOREALI-AMERICANA, or ZOOLOGY of NORTH AMERICA,
containing Descriptions of the Subjects collected in the late Northern
Expeditions under the command of Captain Sir John Franklin, by JOHN
RICHARDSON, M.D., WM. SWAINSON, Esq., and the Rev. WM. KIRBY, published
under the Authority of the Right Hon. the Secretary of State for Colonial
Affairs, _with numerous beautifully coloured plates_, 4 vols. 4to.
(published at 9l 9s) _cloth_, 5l 15s 6d

_The following may be had separately_:

  Vol. 2. Birds, by Swainson, 50 _coloured plates_, (published at 4l 4s)
      _cloth_, 2l 2s

  3. Fishes, by Richardson, _coloured plates_, 1l 4s

  4. Insects, by Kirby, _coloured plates_, 1l 4s

    "We cannot speak in too high terms of admiration with regard to that
    splendid national production the _Fauna Boreali-Americana_. It is
    undoubtedly the best work of its kind that has ever appeared, and will,
    we expect, long remain so."--_Neville Wood._

    "Whether we consider the condensed mass of novel information, the
    number of species for the first time introduced to our systems, the
    accuracy of the scientific details, the beauty and correctness of the
    illustrations and the whole appearance of the book, it reflects the
    highest degree of credit upon the authors, the artist, and the
    government."--_Loudon._

SELBY'S MAGNIFICENT WORK, THE FIGURES OF BRITISH BIRDS, containing an exact
and faithful representation, in their full natural size, of all the known
species found in Great Britain, _383 Figures in 228 beautifully coloured
plates_, 2 vols, elephant folio, (published at 105l) _elegantly hf. bd.
morocco, full gilt back and gilt edges, with glazed paper to the plates_,
31l 10s

1834

---- the same, _plain plates_, (published at 31l 10s) _hf. bd. calf_, 15l
15s

    The grandest work on Ornithology published in this country, the same
    for British Birds that Audubon's is for the birds of America. Every
    figure, excepting in a very few instances of extremely large birds, is
    of the full natural size, beautifully and accurately drawn, with all
    the spirit of life.

    "Every individual of the Falcon and Owl Families would make a PERFECT
    PICTURE OF ITSELF, so beautifully and correctly are they executed: THEY
    HAVE CERTAINLY NEVER BEEN EQUALLED EVEN BY GOULD AND AUDUBON."

    _Ornithologist's Text Book._

    "The author has been most successful, especially in the larger birds,
    and it would be impossible to improve on any of the _Raptores_, which
    for fidelity, boldness, and spirit, are unequalled--every feather is
    distinct, yet beautifully blended."--_Wood's Ornithological Guide._

SELBY'S ILLUSTRATIONS OF BRITISH ORNITHOLOGY, 2 vols. 8vo. Second Edition,
(published at 1l 1s) _in bds._ 12s

1833

    This is the most complete Scientific manual of British Ornithology yet
    published. Every known British Bird is enumerated, with an ample
    description of its plumage, habits, etc., the scientific as well as
    familiar names given by different Naturalists, and references to all
    those who have figured it.

    "SELBY'S IS THE MOST MASTERLY WORK THAT HAS EVER APPEARED ON THE BIRDS
    OF BRITAIN, AND IS QUITE INDISPENSABLE TO EVERY ORNITHOLOGIST."

    _Ornithologist's Text Book._

SOWERBY'S MANUAL OF CONCHOLOGY, containing a complete Introduction to the
Science, illustrated by upwards of 650 FIGURES OF SHELLS, etched on
Copper-plates, in which the most characteristic examples are given of all
the Genera established up to the present time, arranged in Lamarckian
Order, accompanied by copious explanations; observations respecting the
geographical or geological distribution of each; tabular views of the
Systems of Lamarck and De Blainville; a Glossary of technical terms, &c.
&c. NEW EDITION, CONSIDERABLY ENLARGED AND IMPROVED, WITH NUMEROUS
WOOD-CUTS IN THE TEXT, NOW FIRST ADDED, 8vo. _cloth_, 1l 5s

1842

---- the same, COLOURED PLATES, _gilt cloth_, 2l 5s

    This is the only work which, in a moderate compass, gives a
    comprehensive view of Conchology, according to the present advanced
    state of the science. It will not only be found useful to all who wish
    to acquire an elementary acquaintance with the subject, but also to the
    proficient, as a book of reference.

SWAINSON'S ZOOLOGICAL ILLUSTRATIONS, or Original Figures and Descriptions
of New, Rare, or interesting Animals, selected chiefly from the Classes of
Ornithology, Entomology, and Conchology, and arranged on the Principles of
Cuvier and other modern Zoologists, BOTH SERIES COMPLETE, 6 vols. royal
8vo. _containing_ 318 FINELY COLOURED PLATES, (published at 16l 16s)
_unbound_, 8l 8s

---- the same, _very neatly half-bound morocco, uncut,_ 9l 9s

    *** _This fine work was published in parts at 4s 6d each. Either of the
    Series, in 3 vols. may be had separately, at £4. 4s each in parts, or
    £4. 14s 6d half-morocco; but separate Parts can only be sold at the
    original price._

    This highly esteemed publication, by one of the most eminent Zoologists
    of the age, has long been considered very scarce, and from its being
    the sole property of the author has not hitherto been sold under the
    published price. In consequence, however, of his leaving England, he
    has thought it advisable to dispose of the whole stock to the
    advertiser, who now offers the complete copies, which are very few in
    number, at the low prices affixed.

    The whole of the figures are original, having been drawn by Mr.
    Swainson himself, chiefly from specimens in his own collection, and
    coloured under his immediate inspection. They are universally allowed
    to be unrivalled for beauty and fidelity.

    "It might, perhaps, almost be deemed presumption to offer any remarks
    on a work emanating from the pen and pencil of, undoubtedly, the first
    Ornithologist of the day, but we feel it our duty to give our readers
    _some_ idea of the contents of the _Zoological Illustrations._ It will
    be sufficient, if we mention that his coloured figures of birds are
    almost unequalled,--they are certainly not surpassed. The figures are
    beyond conception lovely and delicate, and it only remains for us to
    remark, that EVERY PHILOSOPHIC ORNITHOLOGIST MUST POSSESS THE
    ZOOLOGICAL ILLUSTRATIONS, IF INDEED THEY ARE NOW TO BE HAD."--_Wood's
    Ornithologist's Text Book._

SWAINSON'S EXOTIC CONCHOLOGY, or Figures and Descriptions of Rare,
Beautiful, or Undescribed Shells, with new Letter-press Descriptions, 6
parts, royal 4to. _containing_ 94 LARGE AND BEAUTIFULLY COLOURED FIGURES OF
SHELLS, (published at 5l 5s) _elegantly half-bound morocco, gilt edges_, 2l
12s 6d

Each of the Six Parts may be had separately, at 8s per part.

    "Many of the most rare and beautiful species of this singularly elegant
    genus (the Volutes), have been figured by Swainson in the first plates
    of his _Exotic Conchology_, with a verisimilitude that has never been
    equalled, and probably never will be excelled, by any artist. This
    talent, combined with his scientific knowledge as a naturalist, must
    render the above work the most eminent of its kind in this
    country."--_Dubois._

SWAINSON'S ORNITHOLOGICAL DRAWINGS, being figures of the rarer and most
interesting BIRDS OF BRAZIL. Complete in 7 parts, royal 8vo. CONTAINING
SEVENTY-EIGHT BEAUTIFULLY COLOURED PLATES, (published at 3l 13s 6d)
_elegantly hf. bd. morocco, in one volume_, 2l 5s

    This exceedingly beautiful work is in very few even of the most
    complete ornithological libraries, as only 175 copies were printed, and
    Mr. Swainson refused to sell any excepting to those who had originally
    subscribed for them.

    "Mr. Swainson's name stands so deservedly high, both as an
    ornithologist and an artist, that, in introducing this splendid work to
    the notice of our readers, we shall simply say that we consider it in
    every respect worthy of its author. Farther commendation we feel would
    be superfluous."--_Loudon._

WALLICH, PLANTÆ ASIATICÆ RARIORES, 12 parts, imperial folio, _coloured
plates_, (published at 36l) _sewed_, 25l

WILSON'S AMERICAN ORNITHOLOGY, or Natural History of the Birds of the
United States; with a Continuation by Charles Lucien Bonaparte, Prince of
Musignano, NEW AND ENLARGED EDITION, completed by the insertion of above
One Hundred Birds omitted in the original Work, and illustrated by valuable
Notes, with an interesting Life of the Author, by Sir WILLIAM JARDINE,
Bart., F.R.S.E., F.L.S. 3 vols. 8vo. _with a fine portrait of Wilson, and
97 plates, exhibiting 363 figures of Birds, accurately engraved, and most
beautifully coloured, on glazed drawing paper_, (published at 10l 10s)
_elegantly hf. bd. morocco, top edges gilt_, 4l 4s

1832

    "The valuable Notes and interesting Life of Wilson added to this new
    edition are from the pen of Sir William Jardine, a Naturalist of
    congenial mind in feeling and talent. The plates are better executed
    than those in the American Edition, and the greatest possible attention
    has been paid to accuracy of colouring. Altogether we have rarely seen
    a more valuable work on Natural History, and not one more
    entertaining."--_Literary Gazette._

    "The splendid work of Alexander Wilson will always be regarded as a
    subject of pride by his adopted country, as it certainly is by that
    which gave him birth (Scotland)."--_Chambers._

    "The History of American Birds, by Alexander Wilson, is equal in
    elegance to the most distinguished of our own splendid works on
    Ornithology."--_Cuvier._

    "This is by far the best edition of the American Ornithology, both on
    account of the beautiful plates and the interesting notes of the
    editor. Every ornithologist must, of course, possess the work, and he
    should if possible procure this edition."

    _Neville Wood._

WOODVILLE'S MEDICAL BOTANY, containing Systematic Descriptions of Medicinal
Plants, with a circumstantial Account of their Effects, and of the Diseases
in which they have been most successfully employed, THIRD EDITION, to which
is added a SUPPLEMENTARY VOLUME, by SIR WILLIAM JACKSON HOOKER,
_illustrated by 310 coloured plates by Sowerby_, 5 vols. 4to. (published at
10l 10s) _half-bound morocco, uncut_, 5l 5s

---- The Fifth or Supplementary Volume, entirely by Sir W. J. HOOKER, with
30 Coloured Plates, to complete the old editions, (published at £2. 12s.
6d.) cloth boards, £1. 11s. 6d.

    No well-stored English Library should be without Woodville's Medical
    Botany, a work of long-established reputation, and the best on a
    subject which must, more or less, be interesting to every man of
    inquiry. It contains accurate figures and descriptions of all the
    plants used in English medicine, and is of such authority with
    professional men, as to be almost as essential to them as the
    Pharmacopoeia itself. Subsequent publications of a similar kind, though
    with Woodville as their text-book, have fallen greatly short of the
    original, as well in comprehensiveness of plan, as in accuracy of
    delineation and correctness of colouring. It having long been a matter
    of regret that so excellent a work, from the want of a new edition,
    should remain so much behind the present state of pharmaceutical
    science, Sir William undertook to supply this defect, by adding a
    Supplementary Volume, containing all the new and acknowledged
    discoveries, and all the plants added to the Pharmacopoeias since the
    publication of the work in 1810. New plates have likewise been given
    for the _Cinchonas_, and other plants, which were not properly
    identified in the time of Woodville; and new letter-press or _errata_
    for such descriptions as were deficient or incorrect. All these
    alterations and additions have been given in the supplementary or fifth
    volume, preserving everything contained in the original work, inclusive
    even of the incorrect plates and letter-press, though duplicate,
    leaving it to the purchaser's option either to cancel or retain them,
    as he pleases.

       *       *       *       *       *


_Just Published, in Imperial 8vo. price, Coloured, £1 5s. Plain, 16s._

Part I

OF THE

THESAURUS CONCHYLIORUM,

BY

G. B. SOWERBY, JUN.

Containing descriptions of all the species hitherto known of the following
Genera of SHELLS; Helicina, Pupina, Rostellaria, Aporrhais, Struthiolaria
and Strombus, accompanied by 300 highly finished coloured engravings.

This work is commenced, and will be continued on a more extensive,
complete, and economic plan than has hitherto been attempted. It is
intended to be so complete as to supersede the necessity of keeping an
extensive conchological library, or of consulting a variety of books for
the purpose of identifying species. IT WILL FORM A COMPLETE CONCHOLOGICAL
LIBRARY IN ITSELF.

The vast increase in the number of species, either undescribed or published
in miscellaneous works, and voyages; the difficulty of obtaining such
works, or of naming species without them, and the confusion of Synonymes
which has been the result, are facts which prove the importance of the
present undertaking. The facilities enjoyed by the author, in having access
to several of the most important collections; and obtaining the fullest
information respecting the localities of subjects by those who have sought
them in their native abodes, will, it is trusted, enable him to supply a
generally acknowledged desideratum. He hopes to do this in such a manner as
to fulfil the expectations of his friends, who may rest assured that
neither pains nor expense will be spared to ensure the correctness,
completeness, and beauty of the work.

The plan of the work is as follows:--it will consist of a complete series
of Monographs of Genera of Shells. All the species and varieties of each
genus will be described and figured. The essential characters will be given
in latin. The explanations and general information will be expressed in
English. The figures of average sized shells will be reduced to half the
real diameter; those of larger size will be still further reduced; and
those of small size will be represented of the natural dimensions. The size
of the book is Imperial octavo. The paper, printing, engraving and
colouring of the best description. A part, containing several Monographs
will appear every third month, or oftener if possible, the price of each
part to depend upon the number of figures which it contains, at the rate of
one penny for each figure.

THE 2nd PART WILL APPEAR ON THE 1st OF AUGUST.

       *       *       *       *       *

THE

CONCHOLOGICAL ILLUSTRATIONS,

_Or, figures of hitherto unfigured recent Shells, Part 1 to 200_,

PRICE, 1S. 6D. EACH,

May now be had with Indices complete. None of the Genera contained in this
work will be given in the Thesaurus until all the other Genera are
exhausted.

       *       *       *       *       *

SOWERBY, NATURALIST.

No. 50, GREAT RUSSELL STREET, BLOOMSBURY.

       *       *       *       *       *


CORRECTIONS MADE TO PRINTED TEXT

ANOMIA: "sub-equilateral" corrected from "sub-equilaternal"

ARGONAUTA: "Cephalopoda" corrected from "Cepholopoda"

ib. "the Argonaut is the testaceous part" corrected from "... Agonaut ..."

HALIOTIS: "oblique" corrected from "obilque"

POLYLEPAS: "lepas, rock." corrected from "lepas, Linn."

RHINODOMUS: "No internal groove" corrected from "... grove"

65. "Panopæa Australis" corrected from "... Ausrtalis"

Heading: "Fam. Brachiopoda" corrected from "... Brachipoda"





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