The Pocket Gophers (Genus Thomomys) of Utah

Chapter II: Part 2

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_Remarks._--The mountains of south central Utah are inhabited by pocket gophers that have been designated as _Thomomys talpoides parowanensis_ and _T. t. levis_ by Goldman (1938:334, 336). They are nearly indistinguishable in color and each is variable in cranial details. The diagnostic characters of each form occasionally appear, in varying degrees, throughout the range of the other. The Sevier River Valley separates the ranges ascribed to these two forms. This valley is inhabited by pocket gophers that belong to a different species, _Thomomys bottae_. The ranges of these two races of _talpoides_ converge southward at the headwaters of the Sevier River. Specimens of _parowanensis_ from the northern limits of its range from the Beaver Mountains in eastern Beaver County and those of _levis_ from the northern limits of its range in the Fish Lake Mountains are readily distinguishable from each other. As the ranges converge to the southward, there is progressively more intergradation. The type locality of _parowanensis_ is located in the southern part of its range, while that of _levis_ is in the extreme northern part of its range. Therefore, due to the convergence of the two ranges at the south, the specimens from localities near the type locality of _parowanensis_ show the greatest amount of intergradation, if we regard specimens of _parowanensis_ from the type locality as typical of the race. Four specimens from Webster Flat, sixteen miles east of Cedar City, Iron County, and three from Duck Creek, Cedar Mountains, Kane County could equally well be assigned to either _levis_ or _parowanensis_.

_Specimens examined._--Total, 24, distributed as follows:
_Beaver County_: Britts Meadows, Beaver Mountains, 8,500
ft., 7 (3, M. V. Z.; 2, U. S. N. M.; 2, C. M.); Puffer Lake,
Beaver Mountains, 1 (U. S. N. M.); Kents Lake, Beaver
Mountains, 1 (R. H.). _Iron County_: Lava Beds, 3-1/2 mi. SW
Panquitch Lake, 1 (C. M.); Brian Head, Parowan Mountains, 2
(1, U. S. N. M.; 1, C. M.); Webster Flat, 16 mi. E Cedar
City, 4; Bear Valley, 2 mi. E B. V. Ranger Station, 1 (R.
H.). _Garfield County_: 1/4 mi. W Sunset Point, Bryce
National Park, 8,000 ft., 1 (M. V. Z.). _Kane County_:
Navajo Lake, 3 (R. H.); Duck Creek, Cedar Mountains, 9,000
ft., 3 (1, R. H.).

_Additional records._--_Garfield County_: Panquitch Lake, 1
(see Goldman 1938:335). _Iron County_: Beaver Mountains, 9
(see Bailey, 1915:112); Buckskin Valley, 1 (see Goldman,
1938:335).

=Thomomys talpoides levis= Goldman

_Thomomys fossor levis_ Goldman, Journ. Washington Acad.
Sci., 28:336, July 15, 1938.

_Thomomys talpoides levis_ Goldman, Journ. Mamm., 20:234,
May 14, 1939.

_Thomomys fossor_ Bailey, N. Amer. Fauna, 39:112, November
15, 1915; Barnes, Bull. Univ. Utah, 12 (No. 15):85, April,
1922; Bull. Univ. Utah, 17 (No. 12):102, June, 1927.

_Type._--Female, adult, skin and skull, No. 158079, U. S. National Museum (Biological Surveys Collection); Seven Mile Flat, 5 mi. N Fish Lake, Fish Lake Plateau, 10,000 ft., Sevier County, Utah; October 1, 1908; collected by W. H. Osgood; original number 3616 (after Goldman, type not seen).

_Range._--Fish Lake Mountains in Sevier County south into Garfield County, Utah.

_Diagnosis._--Size medium (see measurements). Color: Upper parts near Sayal Brown, moderately mixed with black, darkest on head and middorsal region, grading to Cinnamon Buff on sides and flanks; underparts Pinkish Buff, clearest on inguinal and pectoral regions; chin, cheeks and nose dusky; postauricular patches large and black; front feet, hind feet and distal half of tail white; ears small and deeply pigmented. Skull: Slender and weak; zygomatic arches not widely spreading; posterior ends of nasals rounded; nasals moderately long and narrow; rostrum long and narrow; extension of premaxillae posterior to nasals short; interparietal usually much wider than long; pterygoid hamulae ridged; interpterygoid space usually narrowly V-shaped; upper incisors short.

_Comparisons._--Compared with topotypes of _Thomomys talpoides moorei_, _levis_ differs as follows: Size smaller; tail shorter. Color: Darker throughout, especially on dorsal surface due to more black of the underfur; underparts deeper buff. Skull: Narrower, less massive; zygomatic processes of maxillae weaker and not as widely spreading; interparietal generally wider; extension of premaxillae posterior to nasals less; posterior ends of nasals rounded rather than emarginate; upper incisors shorter, less procumbent.

Topotypes of _levis_ differ from near topotypes of _Thomomys talpoides uinta_ as follows: Size larger. Color: Upper parts slightly darker; postauricular patches much darker and larger; ears small and deeply pigmented as opposed to large and lightly pigmented; tail darker all around at base, with white part more extensive and with fewer buff-colored hairs. Skull: More convex dorsally; zygomatic arches more widely spreading and angular; nasals longer; rostrum longer; interparietal wider and more elliptical; posterior ends of nasals rounded as opposed to emarginate; extension of premaxillae posterior to nasals less; pterygoid hamulae more ridged; interpterygoid space more narrowly V-shaped; upper incisors shorter and less procumbent.

Topotypes of _levis_ can be distinguished from those of _Thomomys talpoides kaibabensis_ by markedly smaller measurements.

For comparisons with _Thomomys talpoides parowanensis_ and _wasatchensis_ see accounts of those forms.

_Remarks._--Specimens from the Escalante Mountains and the Aquarius Plateau are not typical. They are of approximately the same color as _levis_, but are larger than _levis_ and have cranial details that indicate intergradation with _kaibabensis_ to the south. They resemble _kaibabensis_ in large size, long nasals and widely spreading zygomatic arches, but are like _levis_ in shape of the interparietal, extension of premaxillae posterior to the nasals, rounded posterior ends of nasals, ridged pterygoid hamulae and relatively short upper incisors. Additional material from these regions may prove these animals to merit separation and naming.

_Specimens examined._--Total, 15, distributed as follows:
_Sevier County_: Seven Mile Flat, 5 mi. N Fish Lake, Fish
Lake Plateau, 10,000 ft., 2 (U. S. N. M.); Fish Lake
Experiment Station, 2 (U. S. A. C). _Garfield County_: Posy
Lake, Aquarius Plateau, 2 (B. Y. U.); 18 mi. N Escalante,
9,500 ft., 3; Steep Creek, Boulder-Teasdale Road, Boulder
Mountain, 4 (B. Y. U.); Summit Birch Creek, Escalante
Mountains, 2 (B. Y. U.).

MEASUREMENTS OF ADULT MALES OF THOMOMYS

(In millimeters)

_T. t. gracilis_, 4; topotypes Av. 204 53 28 31.5 13.4 21.7 18.3 6.4 7.6 1.3 15.4 7.2 Min. 194 47 27 30.3 12.9 21.1 17.8 6.3 7.3 1.0 14.7 6.7 Max. 210 63 28 33.5 14.2 22.0 19.0 6.5 7.9 1.7 16.4 7.5

_T. t. oquirrhensis_, 4; topotypes Av. 209 58 28 32.2 13.9 21.9 19.0 6.9 7.6 0.9 15.8 7.7 Min. 197 55 28 31.9 13.7 21.4 18.5 6.7 7.2 0.6 15.5 7.5 Max. 216 60 29 32.8 14.3 22.8 19.5 7.1 7.9 1.0 16.2 7.9

_T. t. wasatchensis_, 10; topotypes Av. 221 67 28 31.3 13.4 21.5 18.9 6.5 7.4 1.1 15.1 7.4 Min. 204 60 26 27.4 11.6 19.1 17.2 6.0 6.6 0.9 14.0 6.7 Max. 237 75 31 34.5 15.2 23.7 20.4 7.3 8.0 2.0 16.5 8.2

_T. t. uinta_, 5; SW slope Bald Peak, Uinta Mts. Av. 199 51 27 31.5 13.1 21.7 19.4 6.3 7.6 1.1 15.2 7.4 Min. 185 47 26 29.6 12.1 20.3 19.0 5.7 7.3 0.7 13.5 7.2 Max. 208 54 28 32.8 13.8 22.2 20.0 6.5 7.8 1.4 15.6 7.6

_T. t. moorei_, 7; topotypes Av. 216 65 29 32.4 13.9 22.9 19.2 6.5 7.7 1.5 15.9 7.3 Min. 203 52 27 31.3 13.0 21.5 18.4 6.0 7.3 0.9 14.8 6.7 Max. 236 72 31 34.7 14.5 23.7 20.0 7.0 8.2 2.0 16.3 7.7

_T. t. fossor_, 8; Cascade Creek, La Plata Co., Colo. Av. 215 61 29 31.7 13.2 21.2 18.7 5.9 7.5 0.6 15.5 7.1 Min. 202 54 27 30.5 12.0 20.5 18.2 5.5 7.0 0.0 14.5 6.9 Max. 228 70 30 33.0 14.4 23.5 19.9 6.3 7.9 1.1 16.9 7.4

_T. t. ravus_, 3; topotypes Av. 248 73 30 35.2 14.6 24.8 21.4 6.3 8.3 2.4 17.1 8.2 Min. 244 70 29 34.5 14.3 23.6 20.5 6.0 8.2 2.2 16.7 8.1 Max. 253 74 30 35.9 15.1 25.7 22.5 6.7 8.4 2.7 17.5 8.5

No. 55270 (U. S. N. M.) _T. t. pygmaeus_, 1; topotype
165 40 20 24.6 10.2 16.3 15.1 5.4 5.9 0.7 12.0 5.7

No. 177506 (U. S. N. M.) _T. t. ocius_, 1; 12 mi. W Linwood,
Henrys Fork, Wyo.
200 62 26 27.5 11.5 19.9 17.8 6.2 6.8 1.0 13.5 7.0

_T. t. parowanensis_, 2; Britts Meadow, Beaver Mountains Av. 215 59 28 34.3 14.5 22.4 18.6 6.0 8.1 1.4 17.3 7.9 Min. 202 48 27 34.1 14.1 22.0 18.4 5.8 8.0 1.0 17.2 7.6 Max. 228 69 29 34.6 14.8 22.7 18.9 6.2 8.2 1.7 17.3 8.2 ----------------------------------------------------------------------

MEASUREMENTS OF ADULT FEMALES OF THOMOMYS

(In millimeters)

_T. t. gracilis_, 2; topotypes Av. 190 58 27 29.7 12.0 19.7 17.3 6.4 7.3 1.2 14.0 6.5 Min. 185 54 27 29.5 11.9 19.7 16.9 6.3 7.2 1.1 14.0 6.4 Max. 194 61 27 29.9 12.0 19.7 17.6 6.5 7.4 1.4 14.0 6.6

_T. t. oquirrhensis_, 7; topotypes Av. 203 56 27 30.2 12.9 20.4 18.2 6.8 7.5 0.8 14.8 7.2 Min. 193 52 25 28.5 12.2 19.5 17.5 6.6 6.7 0.5 14.2 6.9 Max. 215 59 28 31.5 13.3 21.0 19.1 7.2 8.0 1.0 15.5 7.5

_T. t. wasatchensis_, 19; topotypes Av. 205 62 27 31.5 12.7 20.5 18.0 6.5 7.4 0.9 14.6 7.2 Min. 180 52 23 28.1 11.2 19.3 17.2 6.2 6.0 0.6 13.0 6.8 Max. 222 70 30 32.5 14.5 22.0 19.9 6.7 8.1 1.2 16.2 7.5

_T. t. uinta_, 2; SW slope Bald Peak, Uinta Mts. Av. 181 49 25 28.4 11.6 19.8 17.3 6.6 7.2 1.3 13.5 6.8 Min. 177 47 25 28.3 11.6 19.8 17.2 6.4 7.0 1.1 13.3 6.8 Max. 185 50 25 28.4 11.6 19.8 17.4 6.7 7.3 1.5 13.6 6.8

_T. t. moorei_, 5; topotypes Av. 206 62 26 29.9 12.8 21.5 18.4 6.6 7.3 1.3 14.6 6.8 Min. 198 55 24 29.0 12.3 21.0 18.0 6.4 7.0 1.0 14.0 6.4 Max. 213 69 28 31.2 14.1 22.5 19.1 6.8 7.5 1.6 15.6 7.0

_T. t. fossor_, 4; Cascade Creek, La Plata Co., Colo. Av. 215 57 29 32.6 14.2 22.0 19.0 6.0 7.5 0.7 16.2 7.3 Min. 204 51 28 31.3 13.6 21.5 18.0 5.7 7.1 0.5 15.9 7.0 Max. 223 63 30 34.0 14.8 22.9 19.6 6.3 7.8 1.0 16.3 7.5

No. 13684 (C. M.) _T. t. ravus_, 1; topotype
241 71 28 35.7 14.5 24.4 21.5 6.2 7.8 2.7 17.1 8.1

No. 178868 (U. S. N. M.) _T. t. pygmaeus_, 1; Fossil, Wyo.
167 52 20 24.0 10.2 16.5 14.8 5.2 5.6 0.7 11.1 5.8

_T. t. ocius_, 3; topotypes Av. 201 60 25 30.0 13.5 20.5 17.9 6.2 7.2 0.8 15.0 7.4 Min 196 57 25 29.9 13.0 19.9 17.5 6.1 7.1 0.5 14.7 7.3 Max. 205 64 25 30.1 14.0 21.5 18.6 6.3 7.3 1.0 15.3 7.5

_T. t. parowanensis_, 4; Britts Meadow, Beaver Mountains Av. 221 58 29 33.2 14.5 22.8 19.0 6.0 7.8 0.9 15.4 7.3 Min. 207 50 28 30.5 12.8 22.7 18.6 5.8 7.4 0.5 14.7 7.0 Max. 240 66 30 34.8 15.5 23.0 19.6 6.2 8.1 1.5 17.8 7.7

_T. t. levis_, 2; topotypes Av. 203 65 27 28.1 11.1 19.2 17.7 6.1 6.9 0.8 13.0 6.8 Min. 199 61 26 28.0 10.6 18.9 17.5 5.8 6.6 0.6 12.8 6.6 Max. 206 70 27 28.2 11.6 19.5 17.9 6.4 7.2 1.0 13.2 7.0 ----------------------------------------------------------------------

=Thomomys bottae= (Eydoux and Gervais)

_Thomomys bottae_ is a southern species that, within the Great Basin, reaches the most northern limits of its distribution in Utah. The animals of this species inhabit the lower valleys, and with the exception of the Oquirrh Mountains, inhabit also the mountains in that part of the state west of the central mountain ranges. The specific characters are: Sphenorbital fissure present; incisive foramina posterior to infraorbital canal; anterior prism of P4 rounded; interparietal relatively small; lambdoidal suture straight in region of interparietal, in Utah specimens.

=Thomomys bottae aureiventris= Hall

_Thomomys perpallidus aureiventris_ Hall, Univ. California
Publ. Zooel., 32:444, July 8, 1930; Univ. California Publ.
Zooel., 37:3, April 10, 1931.

_Thomomys bottae aureiventris_ Goldman, Proc. Biol. Soc.
Washington, 48:156, October 31, 1935.

_Type._--Male, adult, skin and skull, No. 43980, Museum of Vertebrate Zooelogy, University of California; Fehlman Ranch, 3 mi. N Kelton, 4,225 ft., Box Elder County, Utah; September 27, 1929; collected by Louise Kellogg; original number 451.

_Range._--Northwestern Utah, and extreme western Utah as far south as the southern end of the Deep Creek Mountains.

_Diagnosis._--Size medium (see measurements); claws on front feet small. Color: Near Cinnamon on dorsal and ventral surfaces; inguinal region, front and hind feet and distal third to half of tail white; nose, cheeks and postauricular patches grayish black. Skull: Moderately angular and ridged; zygomatic arches nearly parallel with sides of skull; jugals vertical; marked thickening at union of jugal and zygomatic process of maxilla; greatest zygomatic breadth at anterior part of arches; interpterygoid space lyre-shaped; ventral margin of jugal concave dorsally; nasals long and denticulate distally; parietal ridges bowed in at two places, at coronal suture and at middle of interparietal; paroccipital processes extremely well developed; dorsal frontomaxillary suture usually straight.

_Comparisons._--From near topotypes of _Thomomys bottae centralis_, _aureiventris_ differs as follows: Size larger; tail shorter; hind foot longer; claws on front feet shorter. Color: Slightly darker on upper parts, but with greater extension of white on ventral surface. Skull: Zygomatic breadth greater; greatest width across zygomatic arches at anterior rather than posterior region; zygomatic arches thicker at union of jugals and zygomatic processes of maxillae; dorsal frontomaxillary suture less convex medially; mastoid breadth greater; extension of premaxillae posterior to nasals less; interpterygoid space lyre-shaped rather than V-shaped.

From topotypes of _Thomomys bottae albicaudatus_, _aureiventris_ can be distinguished by: Size larger; hind foot longer. Color: Markedly lighter throughout, Cinnamon as opposed to near (13''''_n_) Black. Skull: Larger in all but three measurements taken; extension of premaxillae posterior to nasals less; alveolar length of upper molar series shorter; zygomatic arches widest anteriorly rather than posteriorly; thickening at union of jugal and zygomatic process of maxilla markedly greater; interpterygoid space lyre-shaped as opposed to V-shaped; lacrimal processes more globose at tips.

_Thomomys bottae aureiventris_ can be readily distinguished from _T. b. bonnevillei_, _sevieri_, _wahwahensis_, and _convexus_ by larger size in all measurements taken and darker coloration. The same differences obtain in comparison with _T. b. tivius_ and _stansburyi_ except that _aureiventris_ is much lighter colored. See comparisons under those forms.

_Remarks._--_T. b. aureiventris_ has one of the most extensive ranges of any race of _T. bottae_ occurring in Utah. The range extends from the valleys of the northwest corner of the state south along the extreme western margin of the state approximately to the southern end of the Deep Creek Mountains. This ascribed range practically bounds the northwest and western margins of the great salt desert in Box Elder and Tooele counties. As far as known, this great waste area harbors no members of the Geomyidae. Pocket gophers were available from four localities in addition to the type locality. In these four localities all of the animals were intergrades. The three specimens from Queen of Sheba Canyon, Deep Creek Mountains, although smaller than _aureiventris_ in every measurement taken, resemble it in color and general configuration of the skull. The animals from Trout Creek and Ibapah at the southern end of the range, although referred to _aureiventris_, are intermediate between it and _centralis_. In color and measurements they more closely resemble _centralis_, but the skulls closely resemble those of _aureiventris_. The skulls show some slight characteristics of _bonnevillei_, the form to the east, which indicate an early relationship between the two. Specimens from the east side of Tecoma Range, adjacent to Pilot Peak, although referred to _aureiventris_ are intergrades between it and _centralis_. Although this locality is nearer the type locality of _aureiventris_ than any of the other record stations, the animals show the maximum departure from topotypes in morphological features. In color they approach _centralis_, and agree with it in one-half of the measured characters. The general configuration of the skull and a majority of the critical diagnostic characters, for example, jugal thickening, are more nearly as in _aureiventris_. From the above remarks it is readily understood that this subspecies is extremely variable.

_Specimens examined._--Total, 55, distributed as follows:
_Box Elder County_: Fehlman Ranch, 3 mi. N Kelton, 4,255
ft., 8 (7, M. V. Z.); Utah-Nevada Boundary, E Side Tecoma
Range, 4,300 ft., 12. _Tooele County_: Ibapah, 5,000 ft.,
21. _Juab County_: Queen of Sheba Canyon, W side Deep Creek
Mountains, 5,600 ft., 11.

=Thomomys bottae robustus= new subspecies

_Type._--Male, adult, skin and skull, No. 2726, Museum of Zooelogy, University of Utah; Orr's Ranch, Skull Valley, 4,300 ft., Tooele County, Utah; June 19, 1938; collected by S. D. Durrant; original number 1583.

_Range._--Skull Valley, Tooele County, Utah.

_Diagnosis._--Size medium (see measurements); tail short; hind foot short. Color: In a series of 24 animals, upper parts vary from Pale Smoke Gray (4 specimens) through Cinnamon Buff (19 specimens) to Dark Mouse Gray (1 specimen). The Cinnamon Buff color is considered to be typical. Color grading to lighter on underparts; postauricular patches small and grayish black; front and hind feet and distal part of tail white. Skull: Small, flat and heavily ridged; nasals short; zygomatic arches heavy and widely spreading, widest posteriorly at union of jugal and squamosal; union of jugal and zygomatic process of maxilla thickened, with a ventrally directed spinous process in sixty percent of the specimens; occasionally there is a second process, also directed ventrally at union of jugal and zygomatic process of squamosal; zygomatic arches convex dorsally; deep dorsal depression present in frontal bones in mature specimens; lacrimal processes prominent, projecting well above the arch at the anteromedial angle of the orbit; interpterygoid spaces V-shaped; tympanic bullae well inflated ventrally; upper incisors short, and pale; when placed on a flat plane the dorsal surface of the skull is nearly parallel to the substratum; space enclosed within the zygomatic arches nearly quadrangular.

_Comparisons._--From topotypes of _Thomomys bottae aureiventris_, _robustus_ can be distinguished as follows: Size smaller; tail and hind foot shorter. Color: Lighter throughout. Skull: Smaller, more heavily ridged and more nearly flat; nasals shorter; rostrum relatively wider and shorter; zygomatic arches shorter and relatively more widely spreading with greatest width posteriorly as opposed to anteriorly; junction of jugal and zygomatic process of maxilla not as prominent; _aureiventris_ shows no spinous process at this junction; lacrimal processes larger and projecting farther dorsally; enclosed space within zygomatic arches roughly quadrangular as opposed to triangular; mastoidal part of tympanic bullae less exposed; sphenorbital fissure smaller; interpterygoid space V-shaped rather than lyre-shaped; palatal pits smaller and shallower; tympanic bullae smaller, but more inflated ventrally; basioccipital averaging relatively wider; molars smaller; upper incisors shorter, smaller and cadmium yellow as opposed to orange yellow.

Comparisons of _robustus_ with topotypes of _Thomomys bottae albicaudatus_ show the following: Size smaller. Color: Lighter throughout; postauricular patches smaller and lighter. Skull: Smaller, more compact and more nearly flat; rostrum shorter and more nearly straight; lacrimal processes larger, projecting higher above the anteromedial angle of the orbit; parietal ridges uniformly heavier; mastoid width actually as well as relatively wider; zygomatic arches heavier and relatively much wider (males 76.2 percent of basilar length, females 73.8 percent as opposed to males 73.8 percent and females 73.5 percent); union of jugal and zygomatic process of maxilla uniformly more thickened; spinous process at jugal-maxillary suture present; zygomatic arches much more concave on ventral surface; uniform deep depression present in mature adults, between frontal processes of premaxillae, and anterior interorbital region of frontals; extension of premaxillae posterior to nasals less; sphenorbital fissure more constricted; tympanic bullae more inflated ventrally, extending well ventrad of basioccipital; palatal pits shallower and smaller; molars smaller; upper incisors shorter, narrower and paler (see comparison of _aureiventris_).

From near topotypes of _Thomomys bottae centralis_ from 1 mile east of Garrison, Millard County, Utah, _robustus_ differs in: Size smaller; tail and hind foot shorter. Color: Lighter, terminal bands of hair cinnamon, but because more black in underfur the animals appear darker; postauricular patches smaller and lighter. Skull: Shorter, more nearly flat and much more heavily ridged; nasals shorter; rostrum shorter and wider; lacrimal processes larger and projecting higher above anteromedial angle of orbit; zygomatic arches heavier, shorter, more angular and actually as well as relatively wider; jugals thicker; angle between maxillary plate and rostrum less obtuse; spinous process at jugal-maxillary suture present; extension of premaxillae posterior to nasals less; parietal ridges much more pronounced; looked at from above, space enclosed within zygomatic arches more quadrangular in shape as opposed to roughly triangular; tympanic bullae more inflated ventrally; molars smaller; upper incisors shorter, narrower and paler.

The characters that distinguish _robustus_ from topotypes of _Thomomys bottae wahwahensis_ are: Size slightly smaller. Color: Darker throughout. Skull: Rostrum longer and narrower; nasals longer; zygomatic arches wider and longer; lacrimal processes larger and projecting higher above anteromedial angle of the orbit; parietal ridges more roughened; tympanic bullae much larger and more inflated ventrally; supraoccipital higher; middorsal depression in frontals present. For comparisons with _Thomomys bottae bonnevillei_ see account of that form.

The remaining forms from the Bonneville Basin, namely, _Thomomys bottae sevieri_, _convexus_, _tivius_ and _stansburyi_ are all easily distinguished from _robustus_. Specimens of _sevieri_ are paler, smaller in every measurement taken, and the skulls are weaker and less angular. All specimens of _convexus_ are paler, the skulls are more convex dorsally and narrower, with less ridging and angularity. Both _tivius_ and _stansburyi_ are small dark forms, with weak, smooth, small skulls as compared with _robustus_ which is light colored and has compact, ridged and angular skulls.

_Remarks._--Twenty-three specimens were obtained at a small isolated spring. Critical study of animals taken only a few miles to the east prove them to be so different as to be referable to another subspecies, _albicaudatus_. _T. b. robustus_ is an endemic form in this desert valley. The variable color is noteworthy but difficult to explain in an isolated population as small as this one. All five of the gray animals are females of which four are lactating adults. The affinities of this subspecies are with _albicaudatus_ to the east, but enough time has elapsed since isolation to enable them to differentiate.

_Specimens examined._--Total, 23, from the type locality.

=Thomomys bottae minimus= Durrant

_Thomomys bottae minimus_ Durrant, Proc. Biol. Soc.
Washington, 52:161, October 11, 1939; Marshall, Journ.
Mamm., 21:154, May 14, 1940.

_Type._--Male, adult, skin and skull, No. 263942, U. S. National Museum (Biological Surveys Collection); Stansbury Island, Great Salt Lake, Tooele County, Utah; June 25, 1938; collected by William H. Marshall; original number 141.

_Range._--Known only from the type locality.

_Diagnosis._--Size small (see measurements); tail relatively long. Color: Upper parts Pinkish Buff, darker on head; underparts Pale Pinkish Buff; front and hind feet white; nose, chin and postauricular patches black. Skull: Long, slender and nearly devoid of ridges; braincase moderately inflated; interparietal quadrangular; zygomatic arches weak, widest in temporal region, but neither widely spreading nor angular; nasals straight and truncate posteriorly; extension of premaxillae posterior to nasals relatively great; tympanic bullae moderately inflated; palatal pits deep; rostrum short but narrow; interpterygoid space moderately lyre-shaped; upper incisors narrow; molars light.

_Comparisons._--Compared with topotypes of _Thomomys bottae albicaudatus_, _minimus_ differs as follows: Size markedly smaller; claws on front feet shorter and weaker. Color: Markedly lighter throughout, being Pinkish Buff as contrasted with near (13''''_n_) Black. Skull: Smaller in every measurement taken; slender, smooth, weak and nonangular as opposed to ridged, robust, wide and angular; zygomatic arches much weaker and not so widely spreading posteriorly; ascending processes of premaxillae much narrower; extension of premaxillae posterior to nasals less; interpterygoid space moderately lyre-shaped as opposed to V-shaped; dentition lighter.

Topotypes of _minimus_ differ from those of _Thomomys bottae aureiventris_ as follows: Size markedly smaller. Color: Lighter dorsally and no "gold color" on underparts. Skull: Markedly smaller in every measurement taken; weak, smooth and slender as opposed to ridged, angular and robust; zygomatic arches weak and widest posteriorly rather than heavy and widest anteriorly; no great thickening at region of union of jugal and zygomatic process of the maxilla; jugals more nearly straight rather than concave laterally; interpterygoid space not so markedly lyre-shaped; dentition lighter.

The races nearest geographically to _minimus_ are _Thomomys bottae nesophilus_ and _T. b. stansburyi_. For comparisons see accounts of those forms.

_Remarks._--This subspecies is the smallest of all the races of _Thomomys bottae_ occurring in Utah. As far as known it is endemic to Stansbury Island, and since the Pleistocene Lake Bonneville attained its highest level has remained on that part of Stansbury Island that was above this high level. (See comments under _nesophilus_.) The sandy nature of the soil and the desert conditions of the area that has since been exposed at lower levels apparently do not constitute a favorable environment. Unlike _nesophilus_ from Antelope Island, this form does not have its affinities with _albicaudatus_, the valley form of the adjacent mainland, but does show affinities with _stansburyi_, the nearest mountain form on the mainland. This is easily understood when one realizes that Stansbury Island is only an isolated part of Stansbury Mountain that projects northward as a peninsula into Great Salt Lake. The history of Stansbury Island with reference to isolation of _minimus_ parallels that of _nesophilus_ on Antelope Island. See discussion under _nesophilus_.

_Specimens examined._--Total, 5, as follows: _Tooele
County_: Stansbury Island, Great Salt Lake, 5 (U. S. N. M.).

=Thomomys bottae nesophilus= Durrant

_Thomomys bottae nesophilus_ Durrant, Bull. Univ. Utah, 27
(No. 2):2, October, 1936; Marshall, Journ. Mamm., 21:156,
May 14, 1940.

_Type._--Male, adult, skin and skull, No. 1136, Museum of Zooelogy, University of Utah; Antelope Island, Great Salt Lake, Davis County, Utah; April 20, 1935; collected by S. D. Durrant; original number 761.

_Range._--Known only from the type locality.

_Diagnosis._--Size medium (see measurements); claws on front feet long. Color: Upper parts Cinnamon Buff; lighter below; sides Pinkish Buff interspersed with gray; pectoral and inguinal regions Cinnamon; nose grayish black; postauricular patches black. Skull: Interparietal wedge-shaped; tympanic bullae small; dorsal surface of lambdoidal prominence 3 mm. wide rather than developed as a crest; jugals nearly straight; zygomatic arches strongly rectangular.

_Comparisons._--Compared with topotypes of _Thomomys bottae albicaudatus_, _nesophilus_ is of approximately the same size, but differs as follows: Claws on front feet longer. Color: Lighter throughout; tail white terminally, but much darker at base; postauricular patches smaller. Skull: Interparietal wedge-shaped as opposed to roughly quadrangular; lambdoidal eminence more of a crest than a ridge; tympanic bullae smaller; jugals more nearly straight; zygomatic arches more nearly rectangular.

From topotypes of _Thomomys bottae aureiventris_, _nesophilus_ differs in: Size smaller; claws on front feet longer. Color: Darker throughout; postauricular patches larger. Skull: Heavier, more massive; zygomatic arches more robust and convex laterally rather than concave; interparietal wedge-shaped rather than roughly quadrangular; braincase more nearly flat; tympanic bullae markedly smaller; upper molariform series longer; molariform teeth wider and heavier; interpterygoid space V-shaped rather than lyre-shaped.

The race nearest geographically to _nesophilus_ is _T. b. minimus_ from Stansbury Island, Great Salt Lake. It can easily be distinguished from _minimus_ by the following features: Size much larger; claws on front feet longer and thicker. Color: Darker throughout; postauricular patches larger and with more admixture of buff colored hairs. Skull: Larger in every measurement taken; wide and robust as opposed to narrow and slender; zygomatic arches more widely spreading and angular; braincase more nearly flat; tympanic bullae actually larger, but relatively smaller; lambdoidal eminence flat-topped rather than a crest; interparietal wedge-shaped as opposed to quadrangular; teeth larger.

_Remarks._--The affinities of _nesophilus_ of Antelope Island are unquestionably with _albicaudatus_ of the eastern and southern mainland. At the time of this writing (1945), Antelope Island is not truly an island, but only the tip of a broad peninsula projecting westward into Great Salt Lake. Nevertheless, the area of occurrence of _nesophilus_ is effectively isolated by the exposed, sandy lake bottom that is unsuited to occupancy by pocket gophers. Fluctuations in the level of the Great Salt Lake have broken and reestablished this connection with the mainland many times. Each of the several other kinds of mammals which are known from both the island and the mainland show no differentiation on the island. These are kinds (see Marshall, 1940:156), which more freely cross the exposed, sandy lake bottom. I, myself, have noted tracks of coyotes going to and from the island. The pocket gopher, _nesophilus_, so far as known is the only mammal which has developed a subspecies endemic to the island. The beach levels of Pleistocene Lake Bonneville are well marked on both Antelope Island and Stansbury Island, which is fifteen miles west of Antelope Island. On the eastern side of Antelope Island the lower beach levels of this prehistoric lake are farmed. Although sought for elsewhere on this island, pocket gophers were found only in the farmed land. On Stansbury Island there has been no farming, and the endemic pocket gophers, _minimus_, although sought for elsewhere on that island were found only above the highest beach levels of the ancient lake. Evidently these pocket gophers still occupy only that part of Stansbury Island that projected above water during the greatest height of Lake Bonneville. Farming on Antelope Island may have developed a more favorable environment for pocket gophers, thus causing them to move down to the lower levels from that part of the island that was above water during Pleistocene times.

_Specimens examined._--Total, 5, from the type locality.

=Thomomys bottae stansburyi= new subspecies

_Type._--Female, adult, skin and skull, No. 2045, Museum of Zooelogy, University of Utah; South Willow Creek, Stansbury Mountains, 7,500 ft., Tooele County, Utah; July 2, 1937; collected by O. S. Walsh and S. D. Durrant; original number 1257 of Durrant.

_Range._--Stansbury Mountains, Tooele County, Utah.

_Diagnosis._--Size small (see measurements). Color: Upper parts Saccardo's Umber, darker on head; sides and underparts Pinkish Buff; nose, chin and postauricular patches black; front and hind feet and distal third to half of tail white. Skull: Small, slender, weak and smooth; zygomatic arches light and not widely spreading; zygomatic arches actually as well as relatively short; interparietal generally quadrangular; nasals relatively long and slender; interpterygoid space narrowly V-shaped; basioccipital fairly wide; tympanic bullae moderately inflated ventrally; dentition light.

_Comparisons._--Topotypical specimens of _stansburyi_ can be readily distinguished from those of _Thomomys bottae centralis_, _aureiventris_ and _albicaudatus_ by being smaller in every measurement taken, particularly those of the skull; the skull is weaker and smoother. In color _stansburyi_ is like _albicaudatus_ but is much darker throughout than _aureiventris_ and _centralis_.

Comparisons of topotypes of _stansburyi_ with those of _Thomomys bottae sevieri_ show them to be of approximately the same size, but to differ as follows: Color: Darker throughout. Skull: Zygomatic arches shorter; tympanic bullae less inflated ventrally; zygomatic breadth less; mastoid breadth greater; width across alveolar processes of maxillae greater; alveolar length of upper molar series greater; molariform teeth larger.

Compared with topotypes of _Thomomys bottae minimus_, _stansburyi_ is seen to be of larger size and darker color throughout, with a skull that is larger in most every measurement taken, although of the same slender, smooth, nonangular type.

Among named races of _Thomomys bottae_, _stansburyi_ most closely resembles tivius, a small, dark, mountain form from central Utah. Size and color are almost the same but _stansburyi_ differs in: Tail shorter; hind foot averaging slightly longer. Skull: Generally larger in every measurement taken; zygomatic arches shorter; width across alveolar processes of maxillae greater; zygomatic arches more widely spreading, and widest in extreme posterior region rather than in region of jugal-squamosal suture.

_Remarks._--The Stansbury Mountains are separated from the Oquirrh Mountains by the Stockton Bar, and from the Onaqui Mountains, which are in reality a continuation of the Stansbury Mountains, by only a low pass. Pocket gophers from Clover Creek, Onaqui Mountains and Little Valley, Sheeprock Mountains, although intergrades between _robustus_ and _albicaudatus_ are dark in color like _stansburyi_. These intergrades are large, dark colored, and have heavy, ridged, angular skulls. It appears that _stansburyi_ is a mountain subspecies derived from _albicaudatus_ of the valley. It would be instructive to artificially transplant gophers from mountains to valleys, and _vice versa_, so as to reveal what effects if any on the animals' morphology the environment might have in one or a few generations. Gophers are well known to be very plastic, and such an experiment as suggested might call for modification of the view, held here, that the differential features of gophers from South Willow Creek and, say, Bauer, are hereditary.

_Specimens examined._--Total, 11, from the type locality.

=Thomomys bottae albicaudatus= Hall

_Thomomys perpallidus albicaudatus_ Hall, Univ. California
Publ. Zooel., 32:444, July 8, 1930; Univ. California Publ.
Zooel., 37:3, April 10, 1931.

_Thomomys bottae albicaudatus_ Goldman, Proc. Biol. Soc.
Washington, 48:156, October 31, 1935; Durrant, Bull. Univ.
Utah, 28 (No. 4):5, August 18, 1937.

_Thomomys perpallidus aureiventris_ Hall, Univ. California
Publ. Zooel., 37:3, April 10, 1931.

_Type._--Male, adult, skin and skull, No. 43971, Museum of Vertebrate Zooelogy, University of California; Provo, 4,510 ft., Utah County, Utah; October 17, 1929; collected by Annie M. Alexander; original number 506.

_Range._--From the area between the Great Salt Lake and the Wasatch Mountains south along the western margin of the central mountains of the state to the Sevier River, in Juab County, west into Tooele County to the Onaqui and Sheeprock mountains.

_Diagnosis._--Size medium (see measurements); claws on front feet medium. Color: Upper parts near (13''''_n_) Black, grading over sides and flanks to Pinkish Cinnamon on underparts; chin, nose, top of head and postauricular patches black; front feet, hind feet and distal third to half of tail white. Skull: Angular and ridged; zygomatic arches moderately wide spreading, widest posteriorly; paroccipital processes weak; zygomatic processes of maxillae convex anteriorly; lacrimal processes small and peglike; jugals convex dorsally on ventral surface; nasals short, rounded distally and truncate proximally; parietal crests bowed in, in two places; interpterygoid space broadly V-shaped.

_Comparisons._-For comparisons of _albicaudatus_ with _Thomomys bottae aureiventris_ and _centralis_ see accounts of those forms.

Topotypes of _albicaudatus_ are dark colored and can be distinguished from those of _Thomomys bottae birdseyei_, _tivius_, _stansburyi_ and _contractus_ which are also dark forms, by larger size and larger, more robust skulls (see accounts of those forms). It can be distinguished from the remainder of the known subspecies of _Thomomys bottae_ in Utah by darker color and by cranial details (see accounts of those forms).

_Remarks._--The range of _albicaudatus_ is larger than that of any other race of _Thomomys bottae_ limited to Utah. Specimens are available from thirty localities which represent widely varied habitats and environments. This subspecies consists of many highly variable local populations, and the marginal populations intergrade freely with adjacent races. In many populations, it is really difficult to recognize the relationships on account of the great variation, and one is frequently tempted to name some of them as distinct. Careful study of the large number of specimens has enabled me to recognize diagnostic characters common to all of these variable populations. The animals range from large and dark at the north to small and light at the south.

The Jordan River bisects Salt Lake County from north to south. Pocket gophers were taken at nine places east of the river, and at three places west of it.

Gophers from Salt Lake City and environs (east of the river) vary in color from almost black to dark cinnamon. Specimens from Draper, which locality is likewise east of the river, are uniformly lighter, but also vary in color. The skulls of animals from both localities are indistinguishable from each other and closely resemble those of topotypes. Specimens from the west side of the river, from Riverton, two miles west of Murray and Rose Canyon, Oquirrh Mountains, all are lighter in color than topotypes. The color varies from darkest at the north at Murray to lightest at the south at Riverton. This is exactly the reverse of what would be expected since Riverton is the locality geographically nearest to the type locality, Provo. The skulls are quite uniform and are all referable to _albicaudatus_. The Jordan River may be one factor which causes this lack of uniformity between the animals from the two sides of the river. Davis (1939:56-57) states that rivers are not barriers to movement of pocket gophers where the river completely freezes over and has the ice covered with thick snow. Although the Jordan River does occasionally freeze over, it is never frozen for more than a few days at a time, and snow in this area does not last for long periods. The material at hand indicates that the gophers from both sides of the river are referable to the same subspecies _albicaudatus_. The animals from the east side of the river are in the aggregate of characters the most typical of _albicaudatus_ of any in the entire range. Those from the west side of the river, although definitely referable to _albicaudatus_ do show some intergradation with _Thomomys bottae robustus_, the subspecies to the west.

The specimens from Bauer, Tooele County, are relatively uniform in color, and are considerably lighter than topotypes of _albicaudatus_. Their upper parts vary from Sepia to Saccardo's Umber as compared with near (13''''_n_) Black of the topotypes. The sides and underparts are lighter, due primarily to much less black in the underfur. They average slightly longer in total length, but shorter in hind foot. All cranial measurements are slightly smaller than in topotypes of _albicaudatus_. The shape of the skull closely resembles that of _albicaudatus_, although the rostrum, nasals, upper incisors and posterior tongues of the premaxillae tend to be narrower. This narrowness indicates intergradation with _Thomomys bottae stansburyi_, the race nearest to the west. These animals are in the majority of characters referable to _albicaudatus_.

Bauer is situated in extreme western Tooele Valley at the foot of Stockton Bar, a low pass between the Stansbury and the Oquirrh mountains. This valley lies to the west of the aforementioned Jordan River. Although these gophers are definitely referable to _albicaudatus_ they are more unlike topotypes than are the animals from Riverton.

The specimens from Settlement Canyon, Oquirrh Mountains, Tooele County, show the same characteristics as those from Bauer.

In a large series of animals from St. John, in Rush Valley, Tooele County, the upper parts vary from black, even darker than topotypes of _albicaudatus_, to Tawny Olive, and the underparts vary from black through Cinnamon Buff to Pinkish Buff. Most of the animals are Cinnamon Buff. Although variable they approach _albicaudatus_ in color. The total length, tail and hind foot of males are longer than in topotypes of _albicaudatus_; females differ in the same direction but only slightly. In both sexes the zygomatic breadth is less, but the mastoid breadth is greater than in _albicaudatus_. In size and shape of the lacrimal processes, and the great thickening of the jugal at the maxillo-jugal suture they approach _robustus_. They are much larger, however, and in the majority of characters are referable to _albicaudatus_.

What has just been said relative to the animals from St. John applies also to those from Clover Creek in the Onaqui Mountains of Tooele County. At the latter locality the tendencies towards _robustus_ are accentuated. This is to be expected, since this locality is midway between St. John and the type locality of _robustus_. All characters considered, these animals are all referable to _albicaudatus_.

The animals from Little Valley, Sheeprock Mountains, Tooele County, resemble _albicaudatus_ in color. They vary on the upper parts from near (1) Sepia to Clay Color, and ventrally from nearly black to Pinkish Buff. They are markedly smaller in every measurement taken, except zygomatic and mastoidal breadths, and extension of premaxillae posterior to nasals. This relatively greater breadth indicates intergradation with _robustus_ to the west. These gophers are smaller in most measurements than any other population referred to _albicaudatus_. This is understandable because gophers from mountains usually are smaller and have weaker, smoother skulls than animals from low lands. Although approaching _robustus_ in size and in some aforementioned cranial details, the aggregate of characters including color, make these animals referable to _albicaudatus_.

The animals from Fairfield, Utah County, are closer geographically to the type locality of _albicaudatus_ than any other series, but morphologically are the least like topotypes. At first glance one is struck with the differences. They are uniformly Clay Color above, with Cinnamon Buff sides and flanks and Pinkish Buff underparts. Their color closely approaches that of _robustus_ to the west which has Cinnamon Buff on the upper parts. Examination of eleven measurements of males and the same number for females, shows that the animals are nearest to _robustus_ in two measurements, to _albicaudatus_ in 12, distinct in 7 and intermediate in one. The general appearance of the skull is intermediate between that of the two above mentioned forms. The differences from _albicaudatus_ in size and color may be correlated with the differences in soil at Fairfield and Provo. At Fairfield the soil is light-colored clay, but at Provo it is sandy and darker. Although they are intergrades between _robustus_ and _albicaudatus_, the animals are referred to the latter race. Utah Lake and its outlet, the Jordan River, make a partial barrier between populations at Fairfield and at the type locality at Provo. During Pleistocene times, when Lake Bonneville was present it formed a complete barrier. Enough time has evidently elapsed since the disappearance of this lake to allow _albicaudatus_, the mainland form, to expand its range to the west. Intergradation has taken place, with the result that the animals from Fairfield, although unstable, agree with the mainland form, _albicaudatus_, in a majority of their characters.

Pocket gophers were taken at four localities from north to south in eastern Juab County. They range in color from Ochraceous Tawny on the upper parts and Cinnamon Buff on the underparts to shades that are slightly lighter. All are much lighter than topotypes of _albicaudatus_. The general configuration of the skull is the same as that of _albicaudatus_, and this is especially true in the females. In the narrower rostrum and weaker dentition they approach _contractus_, but are distinctly lighter colored. Hall (1931:3) referred one specimen from Nephi, Juab County, to _Thomomys bottae aureiventris_. Since that time _Thomomys bottae lenis_ which has some affinities with _aureiventris_ has been described (see account of _contractus_). The large series now available from Nephi and nearby localities do show some intergradation with _lenis_, in that four characters are more as in _lenis_ and _contractus_ and seven characters are more as in _albicaudatus_. Although differing markedly in many respects from topotypes of _albicaudatus_ they fit the aforementioned concept of this subspecies, and are being treated as a variable local population of it.

Provo is the locality listed for specimens which were available to naturalists from 1875-1877. To these specimens the following names were applied: _Thomomys talpoides bulbivorus_ Coues (1875:256; 1877:627) and _Thomomys talpoides umbrinus_ Coues and Yarrow (1875:112). Possibly these names were applied to the animals currently known as _Thomomys bottae albicaudatus_ which does occur at Provo. Without the opportunity to examine the actual specimens, which so far as I know are no longer in existence, I cannot exclude the possibility that the locality designation "Provo" was used in a general sense to include pocket gophers taken a few miles to the eastward of Provo, where it is known that pocket gophers of only the species _Thomomys talpoides_ (current terminology) occur.

_Specimens examined._--Total, 239, distributed as follows:
_Davis County_: Bountiful, 4,500 ft., 1. _Salt Lake County_:
Salt Lake City and environs, 4,300 ft., 51; 2 mi. W Murray,
4,300 ft., 6; Riverton, 4,300 ft., 11; Draper, 4,500 ft., 7;
Rose Canyon, Oquirrh Mountains, 5,650 ft., 4. _Tooele
County_: Bauer, 4,500 ft., 30; Settlement Creek, Oquirrh
Mountains, 6,500 ft., 1; St. John, 4,300 ft., 28; Clover
Creek, Onaqui Mountains, 5,500 ft., 15; Vernon, 4,300 ft., 2
(U. S. A. C.); Little Valley, Sheeprock Mountains, 5,500
ft., 20. _Utah County_: Fairfield, 4,800 ft., 24; Provo,
4,400 ft., 20 (8, B. Y. U.; 12, M. V. Z.). _Juab County_:
Neff Farm, 4 mi. N Nephi, 5,000 ft., 2 (1, R. H.); Nephi,
5,000 ft., 1 (M. V. Z.); 2 mi. S Nephi, 4,700 ft., 14; 7 mi.
SW Nephi, 6,000 ft., 2.

=Thomomys bottae bonnevillei= new subspecies

_Type._--Male, adult, skin and skull, No. 3576, Museum of Zooelogy, University of Utah; Fish Springs, 4,400 ft., Juab County, Utah; June 8, 1940; collected by S. D. Durrant; original number 1955.

_Range._--Known only from the type locality.

_Diagnosis._--Size medium (see measurements); claws on front feet small. Color: Entire dorsal surface Warm Buff; sides near (_e_) Cinnamon Buff, underparts near (16") Pale Pinkish Buff; inguinal region, front and hind feet and distal part of tail white: top of head, nose and cheeks grayish black; postauricular patches small and grayish black; ears small, pointed and with heavily pigmented pinnae. Skull: Angular, short and wide; nasals of medium length, narrow proximally but widely flared distally; interparietal small; lambdoidal suture concave towards the interparietal; zygomatic arches uniformly widely spreading; interpterygoid space widely V-shaped; extension of premaxillae posterior to nasals long; lambdoidal crest well developed.

_Comparisons._--From topotypes of _Thomomys bottae aureiventris_, _bonnevillei_ differs as follows: Size smaller, hind foot shorter. Color: Upper parts and sides lighter; underparts pale buff rather than "gold." Skull: Shorter and relatively wider; rostrum wider and heavier; zygomatic arches relatively wider and more massive, with greatest width posteriorly instead of anteriorly; interpterygoid space widely V-shaped rather than lyre-shaped; thickening at union of jugal and zygomatic process of maxilla less developed; anterior palatine foramina larger; nasals shorter and more markedly flared distally; zygomatic breadth relatively, and mastoidal breadth actually, wider; extension of premaxillae posterior to nasals greater; tympanic bullae more inflated ventrally; upper incisors wider.

From near topotypes of _Thomomys bottae centralis_, from 1 mile east of Garrison, Millard County, Utah, _bonnevillei_ differs as follows: Size smaller; hind foot and tail shorter. Color: Generally darker above and lighter below; top of head darker; postauricular patches smaller and lighter. Skull: Shorter and wider (zygomatic breadth expressed in percent of basilar length being, in males, 74.5 in _bonnevillei_ and 71.5 in _centralis_); interpterygoid space more widely V-shaped; interparietal smaller, and more triangular; nasals shorter and much more dilated distally, as well as more constricted proximally; lacrimal processes smaller and less globuse at tips; temporal fossae larger; braincase and entire dorsal surface of skull more nearly flat; lambdoidal suture convex posteriorly as opposed to nearly straight; tympanic bullae more inflated ventrally.

Comparisons of _bonnevillei_ with the type and type series of _Thomomys bottae wahwahensis_ show them to be of approximately the same size, but to differ as follows: Color: Slightly darker above and lighter below; postauricular patches smaller and lighter. Skull: Larger in every measurement taken, except breadth of rostrum which is smaller; skull not as flat; tympanic bullae more inflated ventrally; nasals and rostrum longer; extension of premaxillae posterior to nasals greater; interparietal smaller and more triangular; zygomatic arches more bowed out laterally; jugals heavier; interpterygoid space more widely V-shaped; upper incisors less massive.

The characters that distinguish _bonnevillei_ from _Thomomys bottae albicaudatus_ are: Size smaller. Color: Markedly lighter throughout. Skull: Shorter and wider; mastoid and zygomatic breadths greater; rostrum narrower but shorter; angle between rostrum and zygomatic processes of maxillae less; interparietal smaller and more triangular; extension of premaxillae posterior to nasals greater; upper incisors shorter, narrower and more recurved.

_T. b. bonnevillei_ is indistinguishable in color from _Thomomys bottae convexus_, but differs from it in the following features: Size larger in nearly every measurement taken. Skull: Flattened dorsally as opposed to convex; zygomatic arches longer and weaker; jugals more nearly perpendicular; tympanic bullae larger; upper incisors longer; alveolar length of upper molar series the same, but molars narrower; rostrum longer but nasals shorter; extension of premaxillae posterior to nasals greater.

Topotypes of _bonnevillei_ can be distinguished from those of both _Thomomys bottae tivius_ and _stansburyi_ by being larger in every measurement taken, by markedly lighter color throughout, and by ridged, massive, angular skulls rather than smooth, weak, nonangular skulls.

The races closest geographically to _bonnevillei_ are _Thomomys bottae robustus_ and _T. b. sevieri_. Compared with topotypes of _robustus_, _bonnevillei_ differs in: Size larger. Color: Lighter throughout. Skull: Larger, although not as compact; zygomatic arches more widely spreading; jugals lighter; lacrimal processes not as prominent; zygomatic processes of maxillae not as robust; nasals more flared distally; extension of premaxillae posterior to nasals greater; alveolar length of upper molar series longer; molars larger; upper incisors longer, wider and darker in color; when placed ventral side down on a surface, the dorsal face of a skull of _robustus_ is approximately parallel to the surface, whereas one of _bonnevillei_ dips down in the occipital region.

_T. b. sevieri_ can be easily distinguished from _bonnevillei_ by being smaller in every measurement taken, darker in color, and by small, weak, smooth skulls as opposed to large, robust, ridged skulls.

_Remarks._--Fish Springs, where _bonnevillei_ occurs is a marshy area south of the barren, salt-desert country of western Utah. The source of water is springs at the base of the north end of the Fish Springs Mountains. Only the moist area supports pocket gophers. Specimens from Trout Creek, Juab County, twenty-five miles to the southwest are intergrades between _bonnevillei_ and _aureiventris_, and are referred to the latter subspecies. The country between Fish Springs and Trout Creek in 1937 and 1940 lacked pocket gophers; it was of the playa and sand type. Probably _T. b. bonnevillei_ was derived from _T. b. aureiventris_, a western mainland form of Pleistocene Lake Bonneville, through isolation and subsequent differentiation morphologically. The moist soils at Cane Springs, seven miles south of Fish Springs, had no pocket gophers when visited in 1940.

_Specimens examined._--Total, 11, from the type locality.

=Thomomys bottae centralis= Hall

_Thomomys perpallidus centralis_ Hall, Univ. California
Publ. Zooel., 32:445, July 8, 1930.

_Thomomys bottae centralis_ Goldman, Proc. Biol. Soc.
Washington, 48:156, October 31, 1935; Hall and Johnson,
Proc. Utah Acad. Sci. Arts and Letters, 15:121, 1938.

_Type._--Male, adult, skin and skull, No. 41688, Museum of Vertebrate Zooelogy, University of California; 2-1/2 mi. E Baker (1-1/4 mi. W Nevada-Utah boundary on 39th parallel), 5,700 ft., White Pine County, Nevada; May 30, 1929; collected by E. Raymond Hall; original number 2683.

_Range._--Extreme western Utah, in Millard, Beaver and Iron counties.

_Diagnosis._--Size medium (see measurements); tail long; claws on front feet long. Color: Near Cinnamon Buff on upper parts, darker in middorsal region, grading to Pinkish Buff on underparts, more accentuated in pectoral and inguinal regions; nose, cheeks and postauricular patches grayish black; front and hind feet and distal half of tail white. Skull: Robust and moderately ridged; zygomatic breadth about the same for entire length of arches; jugals vertical posterior to middle; moderate thickening present at region of maxillo-jugal suture; interpterygoid space narrowly V-shaped; dorsal frontomaxillary sutures convex medially; lacrimal processes globose and well developed; nasals long and with distal denticulations; paroccipital processes well developed.

_Comparisons._--Compared with topotypes of _Thomomys bottae albicaudatus_, _centralis_ differs as follows: Size larger; tail longer; claws on front feet longer. Color: Lighter throughout, Cinnamon Buff as opposed to near (13''''_n_) Black. Skull: Basilar length and length of nasals greater; zygomatic breadth less; zygomatic arches thicker at region of maxillo-jugal sutures; interpterygoid space more broadly V-shaped; dorsal frontomaxillary sutures convex medially as opposed to straight; paroccipital processes more developed; zygomatic arches approximately the same width throughout as opposed to widest posteriorly.

For comparisons with _Thomomys bottae aureiventris_ see account of that form.

_T. b. centralis_ can be distinguished from _Thomomys bottae bonnevillei_, _robustus_, _sevieri_ and _convexus_ by larger size throughout and generally darker color (see accounts of those forms). From _Thomomys bottae stansburyi_ and _tivius_, _centralis_ differs in larger size throughout and lighter color (see accounts of those forms).

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The Pocket Gophers (Genus Thomomys) of UtahChapter II: Part 2

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