Title: Geographic Variation in the Pocket Gopher, Thomys bottae, in Colorado
Author: Youngman, Phillip M.
Language: English
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    UNIVERSITY OF KANSAS PUBLICATIONS

    MUSEUM OF NATURAL HISTORY

    Volume 9, No. 12, pp 363-384, 7 figs, in text, 1 table
    February 21, 1958

    Geographic Variation
    in the Pocket Gopher, Thomomys bottae,
    in Colorado

    BY
    PHILLIP M. YOUNGMAN

    UNIVERSITY OF KANSAS
    LAWRENCE
    1958


    UNIVERSITY OF KANSAS PUBLICATIONS, MUSEUM OF NATURAL HISTORY

    Editors: E. Raymond Hall, Chairman, Henry S. Fitch,
    Robert W. Wilson

    Volume 9, No. 12, pp. 363-384, 7 figs. in text, 1 table
    Published February 21, 1958

    UNIVERSITY OF KANSAS
    Lawrence, Kansas

    PRINTED IN
    THE STATE PRINTING PLANT
    TOPEKA, KANSAS
    1958



Geographic Variation in the Pocket Gopher, Thomomys bottae, in Colorado

BY

PHILLIP M. YOUNGMAN



INTRODUCTION


Two species of pocket gophers of the genus _Thomomys_ (Family Geomyidae)
occur in Colorado, _Thomomys bottae_ (see fig. 1) in the low valleys in
the south-central and southwestern parts of the state and _Thomomys
talpoides_ mainly in the mountains and high valleys.

_Thomomys bottae_ occurs primarily in the Piñon-juniper, Ponderosa Pine,
and Short Grass zones of Daubenmire (1943) but in some localities is
found in the Douglas Fir Zone. _Thomomys talpoides_ occupies primarily
the Douglas Fir Zone and Engelmann Spruce-Subalpine Spruce Zone but is
found also in the Piñon-juniper and Short Grass zones in some
localities.

The ranges of the two species do not overlap in the strict sense but
interdigitate in a parapatric type of distribution.

Two other pocket gophers, _Geomys bursarius_ and _Cratogeomys
castanops_, also occur in Colorado--in the Upper Sonoran Life-Zone.
_Geomys bursarius_ occupies much of the Great Plains, whereas
_Cratogeomys castanops_ is found only on the plains in the southeastern
part of the state.

The objectives of the study, reported on here, were to learn the
geographic distribution of _Thomomys bottae_ in Colorado, to find means
for recognizing the different subspecies, and to describe individual and
geographic variation.

I am indebted to Mr. Sydney Anderson and Professor E. Raymond Hall for
many helpful suggestions and for their critical reading of the
manuscript, to Dr. Richard S. Miller, who made the collection of many of
the specimens possible, and to Dr. Richard M. Hansen for numerous
suggestions. I wish to express my appreciation also to the following for
the loan of specimens in their care: Alfred M. Bailey and A. A. Rogers,
Colorado Museum of Natural History, Denver, Colorado; David H. Johnson,
United States National Museum, Washington, D. C; Robert W. Lechleitner,
Colorado State University, Fort Collins, Colorado; and Robert Z. Brown,
Colorado College, Colorado Springs, Colorado.



METHODS


Adults of approximately equal age were compared in the study of
geographic variation. Three criteria of adulthood are: (a) suture
obliterated between supraoccipital and exoccipital, (b) suture at least
partly obliterated between basisphenoid and basioccipital, (c)
supraorbital crests not widely separated and almost parallel. In males
the crests encroach on the lateral borders of the interparietal; in
females the crests approach the lateral borders of the interparietal but
are more widely separated than in males.

[Illustration: Fig. 1. Geographic distribution of _Thomomys bottae_ in
southwestern Colorado.

    1. _T. b. howelli_
    2. _T. b. aureus_
    3. _T. b. pervagus_
    4. _T. b. cultellus_
    5. _T. b. internatus_
    6. _T. b. rubidus_]

In studying geographic variation, greater emphasis was placed on females
than on males. As noted by Grinnell (1931:4), males vary more than
females, especially in length of rostrum and associated nasal
measurements.

Color terms are those of Munsell (1954). Color measurements were
standardized by the use of a single 100 watt General Electric blue
daylight bulb in a 12 inch white reflector suspended 24 inches above the
specimen. All other light was excluded. The individual hairs of
_Thomomys bottae_ are either bicolored or tricolored. The darkness of a
specimen often may be attributed to the presence of dark-tipped hairs.
The color given in the description is the basic reddish or yellowish
color of the hairs. The presence of a grizzled effect or a dark dorsal
stripe, or any other pattern resulting from dark hairs, is noted in the
remarks.

Specimens examined are listed by counties in the following order:

  Mesa
  Montrose
  San Miguel
  Dolores
  Montezuma
  La Plata
  Archuleta
  Conejos
  Chaffee
  Fremont
  El Paso
  Pueblo
  Custer
  Huerfano
  Alamosa
  Las Animas

Localities are listed from north to south within a county. If two
localities lie on the same line of latitude, the western precedes the
eastern. Localities omitted on the map in order to prevent overlapping
of symbols are in Italics. Unless otherwise indicated, specimens are in
the University of Kansas, Museum of Natural History. The following
initials are used to designate specimens in other collections:

CSU--Colorado State University, Fort Collins, Colorado.

CMNH--Colorado Museum of Natural History, Denver, Colorado.

ERW--E. R. Warren Collection, Colorado College, Colorado Springs,
    Colorado.

USNM--United States National Museum, Washington, D. C.

The following measurements of the skull are listed in the tables:

_Condylobasal length._--The shortest distance between the anteriormost
projections of the premaxillaries and a line touching the posterior
surfaces of the exoccipital condyles.

_Length of nasals._--The distance from the most anterior projection of
the nasal bones to the most posterior projection of a nasal bone.

_Zygomatic breadth._--The greatest distance across the zygomatic arches,
at right angles to the long axis of the skull.

_Squamosal breadth._--The greatest distance between the mastoidal
processes of the squamosal.

_Length of rostrum._--The shortest distance from the shallow notch that
lies lateral to the hamulus of the lacrymal bone, to the tip of the
nasal on the same side of the skull.

_Breadth of rostrum._--The greatest width of the rostrum, anterior to
the maxillae, transverse to the long axis of the skull.

_Alveolar length of upper maxillary tooth-row._--Distance between the
anterior margin of the alveolus of the first cheek-tooth and the
posterior margin of the alveolus of the last upper cheek-tooth, on one
side of the skull.

_Least interorbital breadth._--The least distance across the frontal
bones at the interorbital constriction as seen in dorsal view.



PHYSIOGRAPHY


_Thomomys bottae_ occurs in the Colorado Plateau Province (terminology
of Fenneman, 1931), the Southern Rocky Mountain Province and a small
part of the Great Plains Province.

The Colorado Plateau Province, in the southwestern part of the state, is
mostly above 5000 feet and is characterized by the great number of
canyons cut by rivers and streams in the nearly horizontal strata.
Prominent features of the landscape are cuestas, such as Mesa Verde, and
laccoliths, such as Ute Peak.

The Southern Rocky Mountain Province consists mainly of high granitic
mountains running north and south, many of which extend to more than
14,000 feet above sea level. Included in this region are several large
basins, such as North Park and South Park and the San Luis Valley. The
San Juan Mountains, which separate the Colorado Plateau Province from
the San Luis Valley, and the Sangre De Cristo and Wet mountains, which
intervene between the San Luis Valley and the Great Plains, importantly
influence the distribution of _Thomomys bottae_.

The Great Plains Province is a broad highland that slopes gradually
eastward from the Rocky Mountains. Of importance to the present study
are two subdivisions of the Great Plains, the Colorado Piedmont and the
Raton Section.

The Colorado Piedmont is a much dissected fluviatile plain, roughly
extending from the vicinity of the Arkansas River to the northern
boundary of the state. In general the topography of the Colorado
Piedmont is broadly rolling with greater relief than the high plains to
the east; however, buttes and steep bluffs occur locally.

The Raton Section imperceptibly blends into the southern boundary of the
Colorado Piedmont and extends south into New Mexico and Texas. A
trenched peniplane of greater relief and altitude than the Colorado
Piedmont, it is characterized by high mesas, extensive dissected
lava-capped plateaus, deep canyons, and mountains of volcanic origin.



GEOGRAPHIC VARIATION


Six subspecies of _Thomomys bottae_ occur in Colorado. _T. b. aureus_
and _T. b. howelli_ occupy the Colorado Plateau Province (see fig. 1)
and are characterized by a yellowish color; nasals posteriorly truncate
or rounded; posterior extensions of premaxillae long; basioccipital
wide; and interpterygoid space U-shaped with a median spicule.

_T. b. internatus_, _T. b. cultellus_, and a new subspecies from the
vicinity of Cañon City described on page 376, inhabit the Sangre De
Cristo and Wet mountains in the Southern Rocky Mountain Province and
adjacent parts of the Colorado Piedmont and Raton Section of the Great
Plains Province (see fig. 1). This group of closely related subspecies
is characterized by reddish color; posterior margins of nasals forming a
V; posterior extensions of premaxillae short; basioccipital narrow; and
interpterygoid space V-shaped, lacking a median spicule.

_T. b. pervagus_ occupies part of the San Luis Valley to the west of the
Rio Grande (see fig. 1). In Colorado _T. b. pervagus_ is isolated from
_T. b. internatus_ and _T. b. cultellus_ by the Sangre De Cristo and
Culebra ranges and is separated from _T. b. aureus_ by the San Juan
Mountains. _T. b. pervagus_ occupies an area geographically intermediate
between _T. b. aureus_ to the west and _T. b. internatus_ and _T. b.
cultellus_ to the east and has some characters in common with these
subspecies. _T. b. pervagus_ resembles _T. b. aureus_ in having long
posterior extensions of the premaxillae and in sometimes having rounded
posterior margins of the nasals. _T. b. pervagus_ resembles _T. b.
internatus_ and _T. b. cultellus_ in color, the presence of a V-shaped
interpterygoid space, and a narrow basioccipital. Kelson (1951:69) has
pointed out that in New Mexico the separation of the ranges of _T. b.
pervagus_ and _T. b. cultellus_ is probably complete, but probably
incomplete between _T. b. pervagus_ and _T. b. aureus_. Nevertheless,
the similarities between _T. b. pervagus_ and _T. b. cultellus_ and _T.
b. internatus_ suggest that _T. b. pervagus_ was originally derived from
the more eastern stock.

_T. b. aureus_ is a variable subspecies which, according to Durrant
(1952:211), intergrades with _T. b. howelli_ in Utah. Specimens of _T.
b. aureus_ showing the greatest amount of geographic variation cranially
are from the ecotone between the Piñon-juniper and Douglas Fir zones at
the edge of the range of the subspecies.

_T. b. howelli_ is a markedly distinct subspecies that shows certain
similarities to _T. b. aureus_, but the degree of cranial difference
from _T. b. aureus_ suggests an isolation of long duration, or a rapid
evolution from the parent stock.

_T. b. internatus_ and _T. b. cultellus_ probably intergrade east of the
Sangre De Cristo Range in the vicinity of the Colorado-New Mexico
boundary. The amount of intergradation is obscured by the great amount
of geographic variation occurring in _T. bottae_ at the edge of the
plains and by the lack of specimens from this area.

_T. b. internatus_ is a widespread subspecies showing its greatest
variation at the edge of the plains. This area is an ecotone between the
coniferous forest and the grassland and is by nature an area of change
owing to the alternation of wet and dry periods such as the pluvial,
interpluvial, and postpluvial periods. This seems to support Durrant's
observation (1952:496) that "the greatest range of morphological
variation is in animals from the least stable environments."

Specimens from a small area north of the Arkansas River in the vicinity
of Cañon City (see fig. 1) differ sufficiently from _T. b. internatus_
to be given nominal recognition. High mountains and the Arkansas River
isolate the new subspecies found at Cañon City from populations of _T.
b. internatus_ to the west and south; however there are no apparent
geographic barriers between the newly named subspecies and populations
of _T. b. internatus_ twelve miles to the north or from the vicinity of
Pueblo to the east. This new subspecies is the most extreme of the
variants occurring in the unstable environment at the edge of the
plains.


=Thomomys bottae aureus= Allen

    _Thomomys aureus_ Allen, Bull. Amer. Mus. Nat. Hist., 5:49,
      April, 1893; Warren, Colorado College Publ., 19:252, January,
      1906; Warren, Colorado College Publ., 33:77, January, 1908;
      Warren, Mammals of Colorado, p. 79, 1910; Cary, N. Amer.
      Fauna, 33:136, August 17, 1911.

    _Thomomys bottae aureus_, Goldman, Proc. Biol. Soc. Washington,
      48:156, October 31, 1935; Warren, Mammals of Colorado, p. 158,
      1942.

    _Thomomys apache_ Bailey, Proc. Biol. Soc. Washington, 23:79,
      May 4, 1910. Holotype from Lake La Jara, 7500 feet, Rio Arriba
      County, New Mexico.

    _Thomomys perpallidus aureus_, Bailey, N. Amer. Fauna, 39:74,
      November 15, 1915.

    _Thomomys perpallidus apache_, Bailey, N. Amer. Fauna, 39:75,
      November 15, 1915.

    _Thomomys bottae apache_, Goldman, Proc. Biol. Soc. Washington,
      48:157, October 31, 1935; Warren, Mammals of Colorado, p. 160,
      1942.

    _Thomomys bottae optabilis_ Goldman, Jour. Washington Acad.
      Sci., 26:116, March 15, 1936. Holotype from Coventry, 6500
      feet, Montrose County, Colorado; Warren, Mammals of Colorado,
      p. 159, 1942, part.

  _Holotype._--Adult female, skin and skull number 5243/4123,
  American Museum of Natural History, obtained at Bluff City, San
  Juan County, Utah, May 12, 1892, by Charles P. Rowley.

  _Distribution._--Colorado Plateau Province of southwestern Colorado
  (see fig. 1), northwestern New Mexico, southeastern Utah, and
  northeastern Arizona.

  _Distinctive characters._--Size large (see measurements); usually
  pale in western part of range, dark in eastern part; posterior
  extensions of premaxillae long, wide, and deeply serrated; posterior
  margins of nasals truncate or slightly rounded (see fig. 2);
  interpterygoid space U-shaped, with median spicule; basioccipital
  wide; bullae well inflated, rounded ventrally.

  _Comparisons._--For comparisons with _T. b. howelli_ and _T. b.
  pervagus_, see accounts of those subspecies.

_Remarks._--_T. b. aureus_ is a variable subspecies, which differs
considerably from _T. b. internatus_, _T. b. cultellus_, and _T. b.
rubidus_ and includes several microgeographic races distinguishable to a
taxonomist specializing in the group. These slightly varying populations
are here not considered sufficiently distinct for nominal recognition.

Characters such as color of the pelage and conformation of the bullae
and zygomatic arches vary with the locality, and to some extent vary
among specimens from a single locality.

The name _Thomomys bottae optabilis_, given to specimens from Coventry
by Goldman (1936:116), is here placed in synonymy under _T. b. aureus_
Allen. The characters originally used to describe _T. b. optabilis_ are
of the type that vary between populations only a few miles apart, or
often vary within a population. The skulls of specimens from Coventry
are not lighter in structure than those of _T. b. aureus_. The
premaxillae are not narrower, nor is the frontal region narrower or more
constricted than in _T. b. aureus_.

The name _Thomomys bottae apache_, given to specimens from Lake La Jara,
New Mexico, by Bailey (1910:79), and later applied to specimens from
Colorado by Bailey (1915:75), is here also placed in synonymy under _T.
b. aureus_. Specimens from Lake La Jara, New Mexico, and nearby
localities in Colorado may be separated from topotypes of _T. b. aureus_
on the basis of color only. The topotypes of _T. b. aureus_ are mostly
pale; some, however, are dark. The number of pale specimens in any given
series decreases gradually in a clinal pattern from west to east. Since
there is no noticeable step in the cline and since all specimens show
close cranial similarity, it is felt that nominal recognition of the
darker specimens does not present a realistic picture of the
relationships of the relatively unisolated populations in the Colorado
Plateau Province.

Since _Thomomys bottae_ in the Colorado Plateau Province is especially
plastic, varying from locality to locality, emphasis is here placed on
similarities that unite specimens from different localities. The
individual and microgeographic variations are outlined below.

Specimens from Bedrock have zygomatic arches that are heavy anteriorly.
Specimens from Coventry are dorsally almost uniformly Strong Brown
(7.5YR 5/6) and lack a strong dorsal stripe. The venters are Reddish
Yellow (7.5YR 8/6). Specimens from 15 miles west of Cortez are the
palest specimens of _T. b. aureus_ from Colorado, and closely resemble
topotypes. The basic color varies from Reddish Yellow (7.5YR 7/6 and
6/6) to Strong Brown (7.5YR 5/6). Specimens are marked with a narrow
dark dorsal stripe. The venters are white. Specimens from Ute Peak and
Cortez have Reddish Yellow (7.5YR 6/6) flanks and are slightly darker
dorsally. Many specimens from Mesa Verde are indistinguishable from
specimens from Coventry and from Cortez. Others have dark diffuse dorsal
stripes. The venters are Pink (7.5YR 7/4) or Pinkish White (7.5YR 8/2).
Some specimens from the Mancos River have wide dorsal stripes. Specimens
from three miles west of Durango have especially wide-spreading
zygomatic arches posteriorly and have wide black dorsal stripes. The
venters are Pink (7.5YR 7/4). One specimen from Florida is dark and
grizzled and has a dark dorsal stripe. Another specimen is pale and has
only a small dorsal stripe. Specimens from 12 miles west of Pagosa
Springs have thin rostra and diffuse dorsal stripes. Specimens from
Bondad have a V-shaped interpterygoid space and in it a small median
spicule. One specimen is uniformly grizzled and lacks a dorsal stripe,
giving an overall effect of Dark Yellowish Brown (10YR 3/3). Another
specimen has Strong Brown (7.5YR 5/6) flanks and is only slightly darker
dorsally.

  _Specimens examined._--Total 114. _Colorado_: Montrose Co.: West
  Paradox Valley, 5 (CMNH); Bedrock, 5150 ft., 5 (ERW); Coventry,
  6800 ft., 14 (12 ERW, 2 USNM). San Miguel Co.: 19 mi. N Dove Creek,
  6100 ft., 1. Montezuma Co.: _Ashbaugh's Ranch (T.36N, R.18W) 5350
  ft._, 5 (4 ERW, 1 USNM); 15 mi. W Cortez (Sec. 2, T.35N, R.19W),
  5400 ft., 8; Major Ranch, Cortez, 7 (CSU); _3 mi. SSW Cortez, 6400
  ft._, 1; Ute Peak, 2 (CMNH); Four Corners, 1 (CMNH). Mesa Verde
  National Park: Upper Well, Prater Canyon, 7575 ft., 1; _3/4 mi. S,
  1-3/4 mi. W Park Point, 8000 ft._, 3; _1/4 mi. N Middle Well 7500
  ft._, 1; _Sec. 27, Head of E Fork, Navaho Canyon, 7900 ft._, 2;
  _1-1/4 mi. S, 1-3/4 mi. W Park Point, 8000 ft._, 1; _Middle Well,
  Prater Canyon, 7500 ft._, 9; _3 mi. N Rock Springs, 8200 ft._, 4;
  _1-1/2 mi. S, 2 mi. W Park Point, 8075 ft._, 1; _2-1/2 mi. N, 1/2
  mi. W Rock Springs, 8100 ft._, 3; _2 mi. N, 1/4 mi. W Rock Springs,
  7900 ft._, 2; _1/2 mi. N Far View Ruins, 7825 ft._, 1; _Far View
  Ruins, 7700 ft._, 1; _1 mi. NNW Rock Springs, 7500 ft._, 1; Rock
  Springs, 7400 ft., 1; Mancos River, 6200 ft., 9; _Mesa Verde_, 1
  (USNM). La Plata Co.: 1 mi. N La Plata, 1; 3 mi. W Durango, 5;
  Florida, 6800 ft., 5; Bayfield, 1 (USNM); Bondad, 6 (CMNH);
  Archuleta Co.: 12 mi. W Pagosa Springs, 6700 ft., 2; Arboles, 1
  (USNM). _New Mexico_: Rio Arriba Co.: La Jara Lake, 7500 ft., 2
  (USNM).


=Thomomys bottae howelli= Goldman

    _Thomomys bottae howelli_ Goldman, Jour. Washington Acad. Sci.,
      26:116, March 15, 1936; Warren, Mammals of Colorado, p. 161,
      1942.

    _Thomomys aureus_, Cary, N. Amer. Fauna, 33:136, August 17,
      1911, part.

    _Thomomys perpallidus aureus_, Bailey, N. Amer. Fauna, 39:74,
      November 15, 1915, part.

  _Holotype._--Adult female, skin and skull, number 75684, United
  States National Museum, obtained by Arthur H. Howell at Grand
  Junction, 4600 feet, Mesa County, Colorado, November 7, 1895.

  _Distribution._--Colorado Plateau Province of west-central Colorado
  and east-central Utah, in the Colorado River Valley east of the
  Green River (see fig. 1).

  _Distinctive characters._--Pale (Pinkish White 7.5YR 8/2); cranium
  flattened; nasals short and wide; posterior tongues of premaxillae
  long, thin, and attenuate (see fig. 3).

  _Comparisons._--Compared with _T. b. aureus_, _T. b. howelli_
  differs as follows: paler; nasals shorter and wider; cranium more
  flattened; posterior extensions of premaxillae longer, thinner, and
  more acuminate.

_Remarks._--_T. b. howelli_ most closely resembles _T. b. aureus_;
however, since only one adult specimen of _T. b. howelli_ is known, it
is impossible to appraise adequately its characters. Durrant (1952:211)
records intergradation between _T. b. howelli_ and _T. b. osgoodi_, and
between _T. b. howelli_ and _T. b. aureus_ in Utah.

An attempt to collect specimens of _T. b. howelli_, in March, 1957, by
Richard S. Miller and the writer was unsuccessful.

  _Specimens examined._--Total 2. Mesa Co.: Grand Junction, 4600 ft.,
  1 (USNM); Sieber Ranch, Little Doloris River, 1 (ERW).


=Thomomys bottae pervagus= Merriam

    _Thomomys aureus pervagus_ Merriam, Proc. Biol. Soc.
      Washington, 14:110, July 19, 1901; Cary, Proc. Biol. Soc.
      Washington, 20:26, March 27, 1907; Warren, Colorado College
      Publ., 33:77, January, 1908; Warren, Mammals of Colorado, p.
      79, 1910, part; Cary, N. Amer. Fauna, 33:137, August 17,
      1911, part.

    _Thomomys bottae pervagus_, Goldman, Proc. Biol. Soc.
      Washington, 48:157, October 31, 1935.

    _Thomomys fulvus pervagus_, Bailey, N. Amer. Fauna, 39:82,
      November 15, 1915.

  _Holotype._--Adult male, skin and skull, number 58293, United
  States National Museum, Espanola, Rio Arriba County, New Mexico,
  obtained by J. Alden Loring, January 4, 1894.

  _Distribution._--Upper Rio Grande and San Luis valleys of the
  Southern Rocky Mountains, in northern New Mexico and southern
  Colorado (see fig. 1).

  _Distinctive characters._--Yellowish Red (5YR 4/6); size large (see
  measurements); posterior tongues of premaxillae long, thin, and
  acuminate; nasals long, thin, posterior margins usually forming a
  wide V (see fig. 4); bullae rounded ventrally; interpterygoid space
  V-shaped, lacking median spicule.

  _Comparisons._--From _T. b. aureus_, _T. b. pervagus_ differs as
  follows: reddish, never yellowish or blackish; posterior tongues of
  premaxillae thin and not deeply serrated; posterior margins of
  nasals forming a shallow V; interpterygoid space V-shaped, lacking a
  median spicule; basioccipital narrow. For comparisons with _T. b.
  internatus_, _T. b. cultellus_, and _T. b. rubidus_, see accounts of
  those subspecies.

_Remarks._--_T. b. pervagus_ is a well-defined subspecies. There is
little variation between the topotypes and specimens from Colorado.

  _Specimens examined._--Total 20. _Colorado_: Conejos Co.:
  _Antonito_, 5 (USNM); _7 mi. E Antonito_, 2 (USNM); 12 mi. E
  Antonito, 1 (USNM); Conejos River, 6 mi. W Antonito, 8300 ft., 2
  (USNM). _New Mexico_: Rio Arriba Co.: Espanola, 10 (USNM).


=Thomomys bottae internatus= Goldman

    _Thomomys bottae internatus_ Goldman, Jour. Washington Acad.
      Sci., 26:115, March 15, 1936; Warren, Mammals of Colorado, p.
      160, 1942; Kelson, Univ. Kansas Publ., Mus. Nat. Hist., 5:63,
      October 1, 1951.

    _Thomomys aureus pervagus_, Warren, Mammals of Colorado, p. 80,
      1910, part; Cary, N. Amer. Fauna, 33:137, August 17, 1911,
      part.

    _Thomomys fulvus pervagus_, Bailey, N. Amer. Fauna, 39:82,
      November 15, 1915, part.

  _Holotype._--Adult male, skin and skull, number 150997, United
  States National Museum, obtained at Salida, 7000 feet, Chaffee
  County, Colorado, by Merritt Cary, November 10, 1907.

  _Distribution._--Southern Rocky Mountain Province; southwestern part
  of the Colorado Piedmont, and Raton Section of the Great Plains, to
  the east of the Sangre De Cristo Range (see fig. 1).

  _Distinctive characters._--Yellowish Red (5YR 5/6.5); size medium
  (see measurements); posterior tongues of premaxillae short;
  posterior margins of nasals forming a V (see fig. 6); bullae pointed
  ventrally; interpterygoid space V-shaped, lacking a median spicule;
  basioccipital narrow.

  _Comparisons._--From _T. b. pervagus_, topotypes of _T. b.
  internatus_ differ as follows: uniformly paler, not so reddish;
  smaller; skull smaller; posterior tongues of premaxillae shorter;
  bullae smaller, less inflated, and more pointed ventrally; zygomata
  less angular.

  For comparisons with _T. b. cultellus_ and _T. b. rubidus_, see
  accounts of those subspecies.

_Remarks._--The dividing line between _T. b. internatus_ and _T. b.
cultellus_ is drawn arbitrarily since only one specimen has been
collected between La Veta Pass and the border of New Mexico.

When Goldman (1936:115) named _T. b. internatus_ he included specimens
from Union and Colfax counties, New Mexico, and specimens from Gardner,
Colorado (not Garfield as stated by Kelson, 1951:66). The specimens from
New Mexico and a specimen from Fishers Peak, Colorado, were subsequently
assigned to _T. b. cultellus_ by Kelson (_loc. cit._).

The specimen from Fishers Peak shows some characters that might be
interpreted as intermediate between _internatus_ and _cultellus_, but
shows also some unique characters that can be understood only by further
collecting in the regions north and northeast of the type locality of
_T. b. cultellus_.

Variation is slight in the large series of topotypes of _T. b.
internatus_. Specimens from other localities in the western part of the
range differ little from the topotypes. Specimens from one mile west of
Coaldale have slightly more inflated bullae that are more flattened
ventrally. Specimens from five miles south of Cotopaxi also have the
bullae more flattened ventrally.

Specimens from localities bordering the plains differ from the topotypes
and near topotypes, and in general show greater variation from locality
to locality. Specimens from 12 miles north of Cañon City are dark,
resembling _T. b. rubidus_, but cranially agree with specimens from near
Colorado Springs in being indistinguishable from specimens from Salida.
Specimens from St. Charles Mesa and Bear Creek near Walsenburg differ
from the topotypes in having wider rostra. The specimens from St.
Charles Mesa have more inflated bullae.

  _Specimens examined._--Total 93. Chaffee Co.: 2 mi. NNW Salida,
  7100 ft., 3; _Salida_, 28 (20 ERW, 8 USNM). Fremont Co.: 12 mi. N
  Cañon City, 5; 1 mi. W Coaldale, 8; _Cotopaxi_, 1 (CSU); _5 mi. S
  Cotopaxi_, 12. El Paso Co.: 1-1/4 mi. S Colorado Springs, 2; _9 mi.
  SSW Colorado Springs_, 2; _17 mi. S Colorado Springs_, 1. Custer
  Co.: 2-1/2 mi. S Wetmore, 3; Santa Fe Drive and 20th Lane, Blende,
  1; St. Charles Mesa, 5600 ft., 2 (CSU); Fork of Huerfano and
  Cucharas rivers, 2 (CMNH). Huerfano Co.: 11 mi. WNW Gardner, 7000
  ft., 3; Gardner, 7000 ft., 2 (USNM); 1-1/2 mi. S Redwing, 3; Bear
  Creek, near Walsenburg, 2 (CSU); 1 mi. E La Veta, 8; 5 mi. SE La
  Veta, 2.


=Thomomys bottae cultellus= Kelson

    _Thomomys bottae cultellus_ Kelson, Univ. Kansas Publ., Mus.
      Nat. Hist., 5:64, October 1, 1951.

    _Thomomys fulvus_, Cary, Proc. Biol. Soc. Washington, 20:26,
      March 27, 1907; Warren, Colorado College Publ., 33:76,
      January, 1908; Warren, Mammals of Colorado, p. 80, 1910.

    _Thomomys fulvus fulvus_, Bailey, N. Amer. Fauna, 39:80,
      November 15, 1915.

  _Holotype._--Adult male, skin and skull, number 70919, United
  States National Museum, Halls Peak, Mora County, New Mexico;
  January 13, 1895, obtained by C. Barber.

  _Distribution._--Raton Section of the Great Plains in northern New
  Mexico and extreme southern Colorado (see fig. 1).

  _Distinctive characters._--Dark (topotypes); size medium (see
  measurements); posterior tongues of premaxillae short; posterior
  margins of nasals forming a V (see fig. 5).

  _Comparisons._--From _T. b. pervagus_, topotypes of _T. b.
  cultellus_ differ as follows: darker, not so reddish; smaller; skull
  smaller; zygomatic arches relatively longer; bullae proportionately
  smaller and less inflated; basioccipital proportionately wider;
  posterior tongues of premaxillae shorter.

  Topotypes of _T. b. cultellus_ most closely resemble those of _T. b.
  internatus_ but differ as follows: darker; zygomatic arches more
  widely spreading, not so nearly parallel; nasals not so wide; bullae
  slightly more inflated.

  For a comparison with _T. b. rubidus_ see the account of that
  subspecies.

_Remarks._--Kelson (1951:64) named _T. b. cultellus_ on the basis of six
dark specimens (Dark Reddish Brown 5YR 3/4 and 2/2). Nowhere else within
the range of this subspecies, as defined by Kelson, do any specimens
resemble the topotypes in color.

After comparing topotypes of _T. b. cultellus_ with topotypes of _T. b.
internatus_ of approximately equal age, I disagree with Kelson (_loc.
cit._) on some of the characters which he used to separate _cultellus_
from _internatus_. My findings indicate that _T. b. cultellus_ is not
smaller, that its skull is not smaller and not less angular, and that
the tympanic bullae are not less pointed ventrally. Further collecting
is needed better to limit and diagnose this subspecies.

  _Specimens examined._--Total 13. _Colorado_: Las Animas Co.:
  Fishers Peak, about 8000 ft., 1 (USNM). _New Mexico_: Union Co.:
  Near Folsom, 4 (CMNH); Colfax Co.: Philmont Ranch, Cimarroncito,
  8100 ft., 2. Mora Co.: Halls Peak, 6 (USNM).

[Illustration: Figs. 2-7. Dorsal views of skulls of _Thomomys bottae_. ×
1.

Fig. 2. _Thomomys b. aureus_, 3 mi. W Durango, La Plata Co., Colorado.
No. 72967, Female.

Fig. 3. _Thomomys b. howelli_, holotype, Grand Junction, 4600 ft., Mesa
Co., Colorado. No. 75684 USNM, Female.

Fig. 4. _Thomomys b. pervagus_, Espanola, 5000 ft., Rio Arriba Co., New
Mexico. No. 133614 USNM, Female.

Fig. 5. _Thomomys b. cultellus_, Fishers Peak, 8000 ft., Las Animas Co.,
Colorado. No. 129285 USNM, Female.

Fig. 6. _Thomomys b. internatus_, Salida, 7050 ft., Chaffee Co.,
Colorado. No. 2757 ERW, Female.

Fig. 7. _Thomomys b. rubidus_, holotype, 2-9/10 mi. E Cañon City,
Fremont Co., Colorado. No. 72954, Female.]


=Thomomys bottae rubidus= new subspecies

  _Holotype._--Adult female, skin and skull, number 72954, Museum of
  Natural History, University of Kansas, trapped by Richard S. Miller
  and Phillip M. Youngman, original number 253 (PMY), 2-9/10 miles
  east of Cañon City, 5344 feet, Fremont County, Colorado, March 17,
  1957.

  _Distribution._--Known only from Garden Park in Cañon City and from
  the type locality (see fig. 1).

  _Distinctive characters._--Dark (Reddish Brown 5YR 3/3); size large
  (see measurements); skull large; rostrum wide; zygomatic arches
  rounded and broadly spreading (see fig. 7); alveolar length of upper
  maxillary tooth-row small.

  _Comparisons._--From topotypes of _T. b. internatus_, _T. b.
  rubidus_ differs as follows: uniformly darker; skull averages larger
  in all measurements, except alveolar length of upper maxillary
  tooth-row, which is smaller; rostrum proportionately wider and
  tapered anteriorly; zygomatic arches more rounded; bullae more
  rounded in lateral view.

  Specimens of _T. b. rubidus_ differ from topotypes of _T. b.
  pervagus_ in darker color; rostrum wider posteriorly; posterior
  extensions of premaxillae shorter; bullae smaller, proportionately
  more inflated posteriorly; zygomatic arches more rounded; wider
  across squamosals; alveolar length of upper maxillary tooth-row
  greater.

  From topotypes of _T. b. cultellus_, _T. b. rubidus_ differs as
  follows: paler; larger in all measurements taken; rostrum
  proportionately wider; zygomatic arches more rounded, less angular;
  angle formed by zygomatic arch and rostrum greater; bullae
  proportionately smaller, not so pointed anteriorly; alveolar length
  of upper maxillary tooth-row shorter.

_Remarks._--The range of _T. b. rubidus_ is surrounded by the range of
_T. b. internatus_; nevertheless, intergradation has not been found. For
a discussion of the geographic relation of _T. b. rubidus_ to _T. b.
internatus_ see page 374.

  _Specimens examined._--Total 7. Fremont Co.: Garden Park, Cañon
  City, 5344 ft., 1; _2-9/10 mi. E Cañon City, 5344 ft._, 6.



SUMMARY


A study of 249 specimens of _Thomomys bottae_ from Colorado reveals six
subspecies in the state. _T. b. aureus_ and _T. b. howelli_ occupy the
Colorado Plateau Region in the western and southwestern parts of the
state. _T. b. internatus_, _T. b. cultellus_, _T. b. pervagus_, and the
newly named _T. b. rubidus_ occupy part of the Southern Rocky Mountain
Region and a narrow strip of the Great Plains.

The greatest amount of geographic variation, in _Thomomys bottae_ in
Colorado, occurs in the ecotone between the grassland and coniferous
forest at the edge of the Great Plains, and in the ecotone between the
Piñon, juniper, and sage of the Colorado Plateau and the Coniferous
forest of the southern Rocky mountains.

TABLE 1. MEASUREMENTS, IN MILLIMETERS, OF THOMOMYS BOTTAE

Unless otherwise noted, specimens are adults from Colorado

  Key to Headings:
  A: Catalog number or number of individuals averaged
  B: Total length
  C: Tail
  D: Hind foot
  E: Condylobasal length
  F: Nasal length
  G: Zygomatic breadth
  H: Squamosal breadth
  I: Length of rostrum
  J: Breadth of rostrum
  K: Alveolar length of upper max. tooth-row
  L: Least interorbital breadth

  ===============================================================
  Sex|   [A]   |[B]|[C]|[D]| [E]| [F]| [G]| [H]| [I]| [J]|[K]|[L]
  ---+---------+---+---+---+----+----+----+----+----+----+---+---
     |         | _Thomomys bottae howelli_, holotype
  ---+---------+---+---+---+----+----+----+----+----+----+---+---
   F | 75684[1]|   |   |   |    |    |    |    |    |    |   |
     |  sad.   |219| 71| 29|37.3|11.1|23.7|20.0|14.5| 8.5|7.7|6.6
     |         +---+---+---+----+----+----+----+----+----+---+---
     |         | _Thomomys bottae aureus_, Bedrock
     |         +---+---+---+----+----+----+----+----+----+---+---
   F | 2982[2] |217| 59| 31|40.4|13.8|24.3|20.6|16.7| 8.6|9.2|6.8
   F | 3013[2] |210| 60| 29|38.7|13.0|24.4|20.4|15.7| 8.1|8.9|7.0
     |         |   |   |   |    |    |    |    |    |    |   |
   M | 2997[2] |242| 73| 33|44.7|15.4|28.4|22.8|15.7|10.1|9.0|7.2
  ---+---------+---+---+---+----+----+----+----+----+----+---+---
     |         | Coventry
     |         +---+---+---+----+----+----+----+----+----+---+---
   F | 6 av.   |222| 61| 31|39.0|12.1|25.4|20.3|15.2| 7.8|8.2|6.8
     | Max.    |229| 63| 33|40.0|12.8|25.8|20.6|15.6| 8.2|8.5|7.0
     | Min.    |217| 58| 30|38.3|11.4|25.0|19.3|14.7| 7.5|8.0|6.6
     |         |   |   |   |    |    |    |    |    |    |   |
   M | 3 av.   |259| 70| 35|46.5|15.0|29.3|22.7|17.8| 9.2|9 5|6.7
     | Max.    |270| 76| 36|48.3|16.0|31.9|23.7|18.0| 9.3|9.6|6.9
     | Min.    |250| 65| 35|45.5|14.4|27.6|22.2|17.6| 9.2|8.0|6.4
  ---+---------+---+---+---+----+----+----+----+----+----+---+---
     |         | Ashbaugh's Ranch and 15 mi. W Cortez
     |         +---+---+---+----+----+----+----+----+----+---+---
   F | 7 av.   |225| 67| 28|39.0|13.7|24.4|20.2|16.1| 8.0|8.3|6.3
     | Max.    |238| 75| 31|40.6|14.7|25.0|20.7|16.5| 8.5|8.7|6.8
     | Min.    |216| 55| 26|37.8|12.9|23.6|19.7|15.5| 7.8|7.9|6.1
     |         |   |   |   |    |    |    |    |    |    |   |
   M | 4 av.   |247| 73| 31|44.2|15.9|27.7|22.1|18.6| 9.2|8.4|6.4
     | Max.    |252| 80| 34|45.2|16.7|28.8|22.3|19.8| 9.6|8.8|6.7
     | Min.    |244| 67| 30|43.7|15.5|27.0|21.7|18.0| 8.8|8.0|6.2
  ---+---------+---+---+---+----+----+----+----+----+----+---+---
     |         | Cortez
     |         +---+---+---+----+----+----+----+----+----+---+---
   F | 5120[3] |224| 56| 28|38.1|12.3|....|19.5|15.4| 7.5|7.6|6.5
     | 5121[3] |220| 68| 31|38.3|11.6|24.2|19.6|15.1| 7.6|8.0|6.7
     |         |   |   |   |    |    |    |    |    |    |   |
   M | 5124[3] |257| 81| 33|44.4|15.4|29.5|22.2|18.6| 8.9|8.6|6.5
   M | 5119[3] |215| 62| 28|42.0|14.0|27.9|22.1|17.9| 8.2|8.6|6.4
  ---+---------+---+---+---+----+----+----+----+----+----+---+---
     |         | Mesa Verde (combined)
     |         +---+---+---+----+----+----+----+----+----+---+---
   F | 5 av.   |221| 63| 30|39.0|12.6|24.7|20.2|16.0| 8.0|8.2|6.7
     | Max.    |235| 66| 32|40.4|13.7|25.6|21.1|17.3| 8.7|8.5|7.1
     | Min.    |212| 61| 28|38.1|12.0|24.1|19.5|15.0| 7.7|7.9|6.4
     |         |   |   |   |    |    |    |    |    |    |   |
   M | 3 av.   |246| 74| 32|43.7|14.9|27.8|22.3|18.3| 8.8|8.9|6.6
     | Max.    |252| 79| 33|45.0|15.2|28.4|23.0|18.5| 9.0|9.0|6.8
     | Min.    |238| 69| 31|42.0|14.7|27.5|21.2|18.2| 8.7|8.9|6.3
  ---+---------+---+---+---+----+----+----+----+----+----+---+---
     |         | 1 mi. N La Plata
     |         +---+---+---+----+----+----+----+----+----+---+---
   M | 72966[4]|236| 70| 31|45.4|15.6|29.4|23.3|20.2| 8.8|8.5|6.5
  ---+---------+---+---+---+----+----+----+----+----+----+---+---
     |         | 3 mi. W Durango
     |         +---+---+---+----+----+----+----+----+----+---+---
   F | 3 av.   |225| 65| 28|40.1|13.1|25.7|21.0|16.6| 8.1|8.3|6.5
     | Max.    |230| 67| 29|40.4|13.5|25.8|21.2|16.8| 8.4|8.5|6.6
     | Min.    |219| 63| 28|39.9|13.0|25.7|20.6|16.5| 8.4|8.1|6.4
     |         |   |   |   |    |    |    |    |    |    |   |
   M | 70054[4]|262| 87| 35|45.0|15.6|27.9|22.7|19.7| 9.3|9.8|6.4
   M | 70055[4]|248| 79| 31|43.3|14.0|27.6|22.1|17.1| 8.7|8.2|6.2
  ---+---------+---+---+---+----+----+----+----+----+----+---+---
     |         | 12 mi. W Pagosa Springs
     |         +---+---+---+----+----+----+----+----+----+---+---
   F | 72971[4]|217| 65| 27|39.1|12.8|....|20.0|15.4| 7.4|8.7|6.2
     |         |   |   |   |    |    |    |    |    |    |   |
   M | 72970[4]|238| 70| 29|42.7|15.0|27.5|21.8|17.2| 8.8|8.3|6.5
  ---+---------+---+---+---+----+----+----+----+----+----+---+---
     |         | _Thomomys bottae pervagus_, Antonito
     |         +---+---+---+----+----+----+----+----+----+---+---
   F |133668[1]|   |   |   |    |    |    |    |    |    |   |
     |  sad.   |208| 69| 29|37.3|12.9|23.1|18.2|15.8| 7.5|8.0|6.9
  ---+---------+---+---+---+----+----+----+----+----+----+---+---
     |         | Espanola, New Mexico
     |         +---+---+---+----+----+----+----+----+----+---+---
   F |133616[1]|249| 82| 38|41.1|....|24.6|20.0|16.3| 8.2|8.1|7.1
   F |133619[1]|216| 65| 32|40.6|....|24.9|19.3|....| 8.0|8.0|6.8
     |         |   |   |   |    |    |    |    |    |    |   |
   M | 58293[1]|244| 76| 31|44.0|16.1|26.9|21.2|18.3| 8.8|8.1|6.6
  ---+---------+---+---+---+----+----+----+----+----+----+---+---
     |         | _Thomomys bottae internatus_, Salida
     |         +---+---+---+----+----+----+----+----+----+---+---
   F | 11 av.  |219| 67| 31|38.6|13.4|23.2|19.5|15.4| 7.6|7.8|6.5
     | Max.    |242| 80| 34|40.4|14.2|25.0|20.2|16.2| 8.1|8.4|6.9
     | Min.    |196| 45| 29|37.6|12.9|21.9|18.8|14.8| 7.3|7.0|6.3
     |         |   |   |   |    |    |    |    |    |    |   |
   M | 3 av.   |247| 74| 32|42.9|16.1|25.1|20.9|18.0| 8.2|8.0|6.3
     | Max.    |248| 74| 33|43.7|16.3|26.4|21.7|18.1| 8.8|8.1|6.4
     | Min.    |247| 74| 32|42.2|15.9|25.8|20.5|17.9| 7.9|7.9|6.3
  ---+---------+---+---+---+----+----+----+----+----+----+---+---
     |         | 12 mi. N Cañon City
     |         +---+---+---+----+----+----+----+----+----+---+---
   F | 72945[4]|230| 81| 28|38.1|13.0|22.6|19.4|15.0| 7.9|8.0|6.7
   F | 72947[4]|228| 74| 27|38.7|14.0|23.6|19.8|15.9| 8.2|8.1|6.8
  ---+---------+---+---+---+----+----+----+----+----+----+---+---
     |         | 1 mi. W Coaldale
     |         +---+---+---+----+----+----+----+----+----+---+---
   F | 70042[4]|224| 70| 30|38.1|13.1|23.5|19.5|15.6| 7.7|7.5|6.6
  ---+---------+---+---+---+----+----+----+----+----+----+---+---
     |         | 5 mi. S Cotopaxi
     |         +---+---+---+----+----+----+----+----+----+---+---
   F | 72932[4]|224| 65| 27|39.1|13.8|24.3|20.4|15.5| 7.7|7.5|6.5
     |         |   |   |   |    |    |    |    |    |    |   |
   M | 72925[4]|250| 74| 29|44.0|16.2|27.5|22.8|18.7| 9.0|8.1|6.1
  ---+---------+---+---+---+----+----+----+----+----+----+---+---
     |         | 9 mi. SSW Colorado Springs
     |         +---+---+---+----+----+----+----+----+----+---+---
   F | 72942[4]|225| 77| 29|38.8|14.1|23.3|20.2|15.4| 7.8|8.3|6.7
     | 72943[4]|219| 70| 28|37.7|13.5|23.0|19.7|14.8| 7.6|8.4|6.8
  ---+---------+---+---+---+----+----+----+----+----+----+---+---
     |         | 2-1/2 mi. S Wetmore
     |         +---+---+---+----+----+----+----+----+----+---+---
   M | 70053[4]|250| 81| 30|42.5|16.7|26.3|22.3|17.7| 8.5|7.9|5.9
  ---+---------+---+---+---+----+----+----+----+----+----+---+---
     |         | 200 yards E St. Charles River, 8 mi. W Pueblo
     |         +---+---+---+----+----+----+----+----+----+---+---
   F | 73497[4]|226| 69| 30|39.3|13.9|24.9|20.5|15.7| 7.7|7.9|7.2
   F | 73498[4]|216| 64| 29|38.0|12.9|24.2|20.1|15.1| 7.7|7.4|6.7
  ---+---------+---+---+---+----+----+----+----+----+----+---+---
     |         | St. Charles Mesa
     |         +---+---+---+----+----+----+----+----+----+---+---
   F | 4860[3] |222| 70| 29|38.2|13.5|....|19.3|15.9| 8.2|7.5|6.5
   M | 4864[3] |240| 72| 33|43.1|15.8|....|21.4|17.6| 9.2|7.9|6.7
  ---+---------+---+---+---+----+----+----+----+----+----+---+---
     |         | 11 mi. WNW Gardner
     |         +---+---+---+----+----+----+----+----+----+---+---
   F | 70052[4]|227| 64| 28|37.9|13.0|22.5|18.8|14.8| 7.3|8.0|6.7
  ---+---------+---+---+---+----+----+----+----+----+----+---+---
     |         | 1-1/2 mi. S Redwing
     |         +---+---+---+----+----+----+----+----+----+---+---
   F | 72940[4]|227| 73| 28|39.0|13.1|23.1|18.8|15.6| 7.8|8.0|6.8
  ---+---------+---+---+---+----+----+----+----+----+----+---+---
     |         | 1 mi. E La Veta
     |         +---+---+---+----+----+----+----+----+----+---+---
   M | 70049[4]|254| 88| 32|42.4|15.1|27.5|21.8|17.3| 8.4|8.2|6.5
   M | 70044[4]|239| 80| 32|42.3|16.5|27.8|22.0|17.9| 8.7|8.1|6.4
  ---+---------+---+---+---+----+----+----+----+----+----+---+---
     |         | _Thomomys bottae cultellus_, Fishers Peak
     |         +---+---+---+----+----+----+----+----+----+---+---
   F |129285[1]|   |   |   |    |    |    |    |    |    |   |
     |  sad.   |214| 64| 27|37.2|13.0|....|19.0|15.3| 7.7|7.6|6.5
  ---+---------+---+---+---+----+----+----+----+----+----+---+---
     |         | _Thomomys bottae rubidus_, holotype and topotypes
     |         +---+---+---+----+----+----+----+----+----+---+---
   F | 72952[4]|233| 80| 28|40.6|14.2|25.1|20.8|16.7| 8.8|7.5|6.9
   F | 72954[4]|225| 80| 28|40.3|14.2|24.6|20.6|16.6| 9.2|7.2|6.9
     |         |   |   |   |    |    |    |    |    |    |   |
   M | 3 av.   |261| 89| 31|44.7|15.7|27.8|22.6|18.6|10.1|7.4|6.9
     | Max.    |270| 94| 32|45.1|15.9|28.1|22.7|18.8|10.4|7.6|7.0
     | Min.    |255| 85| 30|44.2|15.5|27.5|22.5|18.5| 9.8|7.2|6.8
  ---+---------+---+---+---+----+----+----+----+----+----+---+---

    sad. denotes subadult.
    1. United States National Museum.
    2. E. R. Warren Collection.
    3. Colorado State University.
    4. Museum of Natural History, University of Kansas.



LITERATURE CITED


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        pls., 10 figs, in text, November 15.

DAUBENMIRE, R. F.

  1943. Vegetational zonation in the Rocky Mountains. Bot. Rev.,
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DURRANT, S. D.

  1952. Mammals of Utah. Univ. Kansas Publ., Mus. Nat. Hist., 6:1-549,
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FENNEMAN, N. M.

  1931. Physiography of western United States. McGraw Hill Book Co.,
        New York, xiii + 534 pp., 173 figs., 1 map in cover pocket.

GOLDMAN, E. A.

  1936. _New pocket gophers of the genus_ Thomomys. Jour. Washington
        Acad. Sci., 26(3):111-120, March 15.

GRINNELL, J.

  1931. A new pocket gopher from southeastern California. Univ.
        California Publ. Zool., 38(1):1-10, 2 pls., October 17.

KELSON, K. R.

  1951. Two new subspecies of Thomomys bottae from New Mexico and
        Colorado. Univ. Kansas Publ., Mus. Nat. Hist, 5(6):59-71, 1
        fig. in text, October 1.

MUNSELL, A. H.

  1954. Munsell soil color charts. Munsell Color Co., Inc., Baltimore.

_Transmitted November 14, 1957._


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