Chapter III: Part 3

_Remarks._--_Thomomys bottae centralis_ has one of the most extensive ranges of any of the known races of _T. bottae_. The eastern limits extend into extreme western Utah. Specimens from Utah for the most part are intergrades between _centralis_ and _aureiventris_, the race to the north. Some minor intergradation is also noted between _centralis_ and _sevieri_ and _bonnevillei_, the races to the east. Intergradation is the expected condition because the animals belonging to _centralis_ are at the extremes of their range in this area. The greater affinities of these animals with _aureiventris_ is to be expected because both _aureiventris_ and _centralis_ are forms of the western mainland of the Pleistocene Lake Bonneville; while the races to the east, although closest geographically, were isolated from the gophers of the western mainland during prehistoric times by this lake. They are still isolated and enough time has elapsed so that only vestiges of morphological intergradation exist between _centralis_ and these eastern forms. Two specimens from Cedar City, Iron County, are intergrades between _Thomomys bottae wahwahensis_, _centralis_ and _planirostris_. Their skulls are slightly convex as in _planirostris_, and the rostrum is short and wide as in _wahwahensis_. In shape of the zygomatic arches, length of the nasals, and color, they resemble _centralis_ to which they are here referred.

_Specimens examined._--Total, 49, distributed as follows:
_Millard County_: 1 mi. SE Gandy, 5,000 ft., 15 (M. V. Z.);
White Valley (Tule Spring), 60 mi. W Delta, 4, (3 in R. W.
Fautin Vertebrate Collection); Robison Ranch, 5,300 ft., (on
Hendry Creek) Simonsons Ranch, 4,596 ft., 2 (M. V. Z.); 1
mi. E Garrison, 5,000 ft., 21; 5 mi. S Garrison, 5,400 ft.,
5 (M. V. Z.). _Iron County_: Cedar City, 2 (M. V. Z.).

=Thomomys bottae sevieri= new subspecies

_Type._--Female, adult, skin and skull, No. 2530, Museum of Zooelogy, University of Utah; Swasey Spring, House Mountains, 6,500 ft., Millard County, Utah; May 16, 1938; collected by S. D. Durrant; original number 1380.

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

_Diagnosis._--Size medium (see measurements); claws on front feet short and weak; ears short; tail relatively long. Color: Upper parts Pinkish Buff, grading over sides to Pale Pinkish Buff on underparts; nose, top of head, chin and cheeks grayish black; postauricular patches small and grayish black; front and hind feet and distal two-thirds of tail white. Skull: Small, weak and smooth; rostrum narrow; nasals narrow, not markedly flared distally; zygomatic arches weak, not angular, and of "graceful" contour; lacrimal processes small; characteristic dorsal depression present in region of sagitto-coronal suture; mastoid and zygomatic breadths narrow; occiput narrow and high; braincase well inflated; paroccipital processes small and smooth; interpterygoid space narrowly V-shaped; tympanic bullae small, but well inflated ventrally; alveolar length of upper molar series short; molars small; upper incisors short, but narrow.

_Comparisons._--From topotypes of _Thomomys bottae aureiventris_, _sevieri_ differs as follows: Size smaller. Color: Lighter throughout, no "gold" on underparts. Skull: Much smaller in every measurement taken, less massive and not angular; zygomatic arches weaker and widest posteriorly rather than anteriorly; union of jugal and zygomatic process of maxilla not greatly thickened; interpterygoid space narrowly V-shaped rather than lyre-shaped; pterygoid hamulae shorter and weaker; tympanic bullae smaller, but markedly more inflated ventrally; dentition smaller and weaker.

From near topotypes of _Thomomys bottae centralis_, _sevieri_ can be distinguished by the following features: Size markedly smaller. Color: Lighter throughout. Skull: Markedly smaller in every measurement taken, weaker and smoother; zygomatic arches weaker, less angular and more "graceful"; rostrum shorter, but narrower; lacrimal processes smaller; tympanic bullae smaller, but more inflated ventrally, being triangular in shape as opposed to ovate and with anteromedial margin decidedly pointed; pterygoid hamulae smaller and weaker; dentition smaller and weaker.

_T. b. sevieri_ can readily be distinguished from _Thomomys bottae albicaudatus_ by the following features: Size smaller in every measurement taken. Color: Markedly lighter throughout. Skull: Smaller, and weaker; rostrum shorter and narrower; ascending processes of premaxillae narrower; extension of premaxillae posterior to nasals shorter; posterior tongues of premaxillae narrower; dentition much lighter.

Comparisons of _sevieri_ with topotypes of _Thomomys bottae wahwahensis_ show them to be of approximately the same size, but to differ as follows: Hind foot longer; ear shorter. Color: Slightly darker. Skull: Smaller, weaker, less ridged; zygomatic breadth less; zygomatic arches markedly less angular; mastoid breadth less; rostrum much longer and narrower, not as blunt nor flattened; tympanic bullae much larger and more inflated ventrally; braincase vaulted as opposed to flattened.

From topotypes of _Thomomys bottae bonnevillei_, _sevieri_ differs in: Size smaller throughout. Skull: Smaller in every measurement taken, weaker, smoother and less angular; dentition smaller and weaker.

Topotypes of _sevieri_ are easily distinguished from those of _Thomomys bottae robustus_ by smaller size, and smaller, markedly weaker skull which is less angular and ridged.

Among named races of _Thomomys bottae_, _sevieri_ is closest geographically to _convexus_, but differs from it as follows: Size larger; hind foot longer. Skull: Smaller in every measurement taken; nasals shorter and not so flaring distally; rostrum weaker, narrower and not so depressed; zygomatic arches markedly weaker and less angular; lacrimal processes smaller; supraoccipital narrower and higher; paroccipital processes weaker; tympanic bullae smaller; dentition markedly weaker.

Topotypical specimens of _sevieri_ can be readily distinguished from those of _Thomomys bottae tivius_ by Pinkish Buff instead of Mummy Brown on upper parts. Tympanic bullae larger and markedly more inflated; nasals longer; zygomatic and mastoidal breadths greater; rostrum longer and more depressed; upper incisors longer and wider; molariform teeth smaller. The skulls of _sevieri_ resemble those of _tivius_ more closely than those of any other subspecies.

_Remarks._--The House Mountains in western Millard County are surrounded by desertlike terrain that is seemingly unsuited to pocket gophers. In these mountains, gophers were sought in vain at several localities, including Antelope Springs which superficially appeared suitable for the animals. Pocket gophers were found only at the type locality, Swasey Spring, which is well above the highest level of the Pleistocene Lake Bonneville. _T. b. sevieri_, like _T. b. minimus_ on Stansbury Island, Great Salt Lake, appears to remain only on land that was an island when Lake Bonneville was at its highest level.

_Specimens examined._--Total, 10, from the type locality.

=Thomomys bottae convexus= Durrant

_Thomomys bottae convexus_ Durrant, Proc. Biol. Soc.
Washington, 52:159, October 11, 1939.

_Type._--Male, adult, skin and skull, No. 2482, Museum of Zooelogy, University of Utah; E side Clear Lake, 4,600 ft., Millard County, Utah; May 20, 1938; collected by S. D. Durrant; original number 1401.

_Range._--Westcentral Utah in Delta Valley.

_Diagnosis._--Size medium (see measurements). Color: Upper parts and sides Pinkish Buff, purest on sides; underparts Pale Pinkish Cinnamon; inguinal and pectoral regions Pale Pinkish Buff; nearly all specimens have white on perineal region; nose grayish black; front feet, hind feet and distal third to half of tail white; postauricular patches black. Skull: Braincase moderately convex on dorsal surface; rostrum strongly depressed, giving the entire dorsal surface of the skull a "rocker-shape"; zygomatic arches heavy, short and widely spreading, widest posteriorly; upper incisors recurved, short and wide; molariform teeth large; alveolar length of upper molar series long; palatal pits deep; tympanic bullae moderately inflated ventrally; mastoidal breadth actually as well as relatively wide.

_Comparisons._--Compared with topotypes of _Thomomys bottae wahwahensis_, _convexus_ is of approximately the same color, but differs as follows: Size smaller; tail, hind foot, and ear shorter. Skull: Rostrum longer, narrower and more depressed; skull convex rather than flat; nasals longer, and convex rather than flat; tympanic bullae larger; zygomatic arches shorter and more massive; molariform teeth larger.

From topotypes of _Thomomys bottae centralis_, _convexus_ differs in: Size smaller; tail and hind foot shorter. Color: Uniformly lighter, more white in perineal region. Skull: Smaller, more convex; rostrum shorter, wider and more depressed; zygomatic arches shorter and heavier; mastoidal breadth actually, as well as relatively wider; tympanic bullae more inflated ventrally; upper incisors shorter and wider.

Comparatively, topotypes of _convexus_ can be distinguished from those of _Thomomys bottae aureiventris_ by: Size smaller; tail and hind foot shorter. Color: Darker on upper parts; no "gold" on underparts. Skull: Smaller and more nearly flat; rostrum shorter and more depressed; zygomatic arches shorter, heavier and widest posteriorly rather than anteriorly; interpterygoid space V-shaped as opposed to lyre-shaped; upper incisors shorter, narrower and more recurved.

Topotypical specimens of _convexus_ differ from those of _Thomomys bottae nesophilus_ as follows: Size smaller; tail and hind foot shorter. Color: Uniformly lighter throughout, Cinnamon Buff as opposed to Pinkish Buff. Skull: Smaller; rostrum heavier, shorter and more depressed; zygomatic arches shorter, heavier and not so widely spreading; no widening of supraoccipital as in _nesophilus_; upper incisors shorter and more recurved.

When compared with topotypes of _Thomomys bottae albicaudatus_, _convexus_ shows the following differences: Size smaller; tail and hind foot shorter. Color: Markedly lighter throughout. Skull: Smaller, more convex and compact; rostrum shorter, heavier, more depressed and compact; zygomatic arches shorter and more robust; upper incisors shorter and more recurved.

_Thomomys bottae tivius_ is the race closest geographically to _convexus_. From it, _convexus_ can be readily distinguished by: Size larger; tail shorter; hind foot longer. Color: Markedly lighter throughout. Skull: Much heavier and more compact, weights of skulls of males and females of the two subspecies being 2.4 grs., 1.6; 1.6, 1.2, respectively; rostrum heavier, wider and more depressed; zygomatic arches shorter, and more massive; upper incisors shorter, wider and more recurved; molariform teeth larger.

For comparisons with _Thomomys bottae lenis_, _contractus_, _sevieri_, _bonnevillei_, and _robustus_ see accounts of those forms.

_Remarks._--_T. b. convexus_ is limited to the area around Clear Lake in Millard County. This lake is surrounded by areas of loose, shifting sand and flat areas of barren alkali. The lake is fed by springs which flow from lava outcroppings on its eastern side. As far as discernible, the only area populated by pocket gophers (1938) was that adjacent to the lake where vegetation had trapped the sand. The factor which limits the extension of range of this subspecies probably is plant food. Also, the soil is mechanically poor for burrowing, since it caves in easily and burrows were found only in the sand where salt grass (_Distichlis stricta_) had trapped and stabilized it. Burrows were found from the edge of the water back as far as this grass persisted.

_Specimens examined._--Total, 17, from the type locality.

=Thomomys bottae tivius= Durrant

_Thomomys bottae tivius_ Durrant, Bull. Univ. Utah, 28 (No.
4):5, August 18, 1937.

_Type._--Female, adult, skin and skull, No. 1827, Museum of Zooelogy, University of Utah; Oak Creek Canyon, 6 mi. E Oak City, 6,000 ft., Millard County, Utah; September 14, 1936; collected by S. D. Durrant; original number 1100.

_Range._--Limited to the Canon Mountains, Millard County.

_Diagnosis._--Size small (see measurements). Color: Upper parts Mummy Brown, grading through Cinnamon on the sides to Pale Cinnamon on the underparts; cheeks Cinnamon; postauricular patches black; distal third to half of tail white. Skull: Small, weak; zygomatic arches weak, not widely spreading, widest posteriorly; tympanic bullae large; interpterygoid space V-shaped; nasals short, usually simple distally, but with some denticulations in some specimens; palatal pits deep; palate narrow; paroccipital processes small; incisors, both upper and lower, narrow; molariform teeth small.

_Comparisons._--Topotypes of _tivius_ differ from those of _Thomomys bottae albicaudatus_ as follows: Size markedly smaller in every measurement taken. Color: Lighter, Mummy Brown as opposed to near (13''''_n_) Black. Skull: Smaller, slenderer and weaker; zygomatic arches weak and not widely spreading as opposed to massive and wide spreading; nasals and rostrum narrower and shorter; extension of premaxillae posterior to nasals shorter; tympanic bullae smaller; molariform teeth smaller.

For comparisons with _Thomomys bottae stansburyi_ and _T. b. contractus_ see accounts of those forms.

The four subspecies _tivius_, _albicaudatus_, _stansburyi_, and _contractus_ are the darkest in color of all the _Thomomys bottae_ occurring within the state.

_Remarks._--This small, dark subspecies is limited to the Canon Mountains in eastern Millard County. Apparently it is a mountain derivative of _Thomomys bottae contractus_ which occurs in the valleys to the east and west of these mountains. Intergradation is noted with animals from the valleys on either side. For further comments on distributional problems of this type see remarks under _Thomomys bottae stansburyi_.

_Specimens examined._--Total, 12, from the type locality.

=Thomomys bottae contractus= new subspecies

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

_Thomomys bottae albicaudatus_ Durrant. Bull. Univ. Utah, 28
(No. 4):4, August 18, 1937.

_Type._--Male, adult, skin and skull, No. 1851, Museum of Zooelogy, University of Utah; Scipio, 5,315 ft., Millard County, Utah; September 17, 1936; collected by S. D. Durrant; original number 1125.

_Range._--Extreme eastern Millard and Beaver counties, Utah.

_Diagnosis._--Size medium (see measurements). Color: Upper parts Cinnamon Buff, mixed with black giving a color of Dresden Brown; sides between Cinnamon Buff and Pinkish Buff; underparts Pinkish Buff, purest on inguinal and pectoral regions; postauricular patches medium in size and black; ears covered with black hairs; nose, chin, cheeks and top of head dusky; front feet, hind feet and distal third to half of tail white; proximal part of tail covered all around with buff-colored hairs. Skull: Long, slender, moderately ridged and convex transversally at proximal ends of nasals; nasals long; rostrum long and narrow; posterior ends of nasals truncate or shallowly emarginate; ascending processes of premaxillae slender; extension of premaxillae posterior to nasals long; zygomatic arches neither robust nor widely spreading; interparietal subquadrangular; supraoccipital extending horizontally well behind lambdoidal suture instead of dropping off abruptly to the foramen magnum; interpterygoid space moderately V-shaped in some specimens, but somewhat lyre-shaped in others; tympanic bullae large and truncate anteriorly; upper incisors long and narrow; molariform teeth small and light.

_Comparisons._--Compared with topotypes of _Thomomys bottae albicaudatus_, _contractus_ differs as follows: Tail longer. Color: Lighter throughout. Skull: Slenderer, less ridged and angular; rostrum narrower; zygomatic and mastoidal breadths less; ascending processes of premaxillae narrower; posterior tongues of premaxillae narrower; posterior ends of nasals less truncate; zygomatic arches weaker, less angular, and less widely spreading posteriorly; interparietal larger; paroccipital processes weaker; interpterygoid space not as widely V-shaped; upper incisors longer and narrower; molariform teeth smaller.

Topotypes of _contractus_ can be distinguished from those of _Thomomys bottae convexus_ by the following: Size larger, tail longer; hind foot larger. Color: Darker throughout. Skull: Longer, narrower, and not as massive; top of skull moderately, as opposed to strongly, convex; nasals arched rather than straight; zygomatic arches neither as widely spreading, angular nor massive; space enclosed within zygomatic arches longer; interparietal larger; interpterygoid space more narrowly V-shaped; upper incisors longer and narrower; molariform teeth much lighter.

Comparisons of topotypes of _contractus_ with near topotypes of _Thomomys bottae centralis_ show them to be approximately the same size, but to differ as follows: Color: Darker throughout. Skull: Shorter and slenderer; rostrum narrower; region between posterior tongues of premaxillae narrower and more convex transversally; nasals more truncate; zygomatic breadth less, but arches relatively more widely spreading posteriorly; interparietal larger; interpterygoid space generally narrower; upper incisors longer and narrower; molariform teeth smaller.

Topotypes of _contractus_ differ from those of _Thomomys bottae aureiventris_ as follows: Size smaller; tail longer; hind foot shorter. Color: Darker throughout. Skull: Shorter but slenderer; rostrum narrower; nasals shorter but slenderer, and more truncate posteriorly; extension of premaxillae posterior to nasals longer; zygomatic arches weaker and less angular; zygomatic processes of maxillae weaker and with no marked thickenings at union of maxilla and jugals; interparietal larger; interpterygoid space more generally V-shaped; upper incisors longer and narrower; molariform teeth smaller.

Compared with topotypes of _Thomomys bottae planirostris_, _contractus_ differs in: Size smaller throughout. Color: Darker, more black and less Cinnamon in pelage. Skull: Smaller in every measurement taken; rostrum narrower; nasals arched instead of flat; zygomatic arches neither angular, massive nor widely spreading; upper incisors narrower; molariform teeth markedly smaller and weaker.

Topotypes of _contractus_ differ from those of _Thomomys bottae levidensis_ in larger size, darker color and longer, slenderer skulls.

Among named races of _T. bottae_, _contractus_ is closest morphologically to _tivius_. It differs from it as follows: Size larger throughout. Color: Lighter throughout. Skull: The same general shape and proportions, but larger in every measurement taken; rostrum longer and narrower; extension of premaxillae posterior to nasals longer; posterior tongues of premaxillae narrower.

_Remarks._--Fifteen animals from Oak City are intergrades between _contractus_ and _tivius_. Intergradation with _lenis_ is also shown in some specimens by the widely spreading zygomatic arches. In the majority of characters including the diagnostic long, slender, narrow rostrum they are more like _contractus_ to which they are here referred.

Nine animals from Beaver were considered by Hall (1931:3) and Durrant (1937:4) to be intergrades between _Thomomys bottae albicaudatus_ and _Thomomys bottae centralis_. Restudy of these specimens in the light of additional material now shows them to be intergrades between _T. b. centralis_, _T. b. planirostris_ and _T. b. contractus_. The majority of these animals are intermediate in color between _centralis_ and _contractus_, but a few have the reddish cast of _planirostris_. The shape of the nasals is characteristic of _planirostris_, while the zygomatic arches are as in _centralis_. In the remainder of the diagnostic characters they are like _contractus_ to which they are here referred.

Strong affinities exist between _albicaudatus_, _tivius_ and _contractus_. All three of these races probably stemmed from a dark form which formerly inhabited the eastern mainland of the Pleistocene Lake Bonneville. At present, _tivius_ is isolated on the Canon Mountains in eastern Millard County, while the range of _albicaudatus_ and _contractus_ have been separated by that of _lenis_. _T. b. lenis_ has the majority of its affinities with _aureiventris_ which is an inhabitant of the western mainland of this ancient lake. An understanding of the history of the Sevier River Valley will probably clarify this distribution of pocket gophers.

_Specimens examined._--Total, 39, distributed as follows:
_Millard County_: Oak City, 5,000 ft., 15; Scipio, 5,315
ft., 15. _Beaver County_: Beaver, 6,000 ft., 9 (M. V. Z.).

=Thomomys bottae lenis= Goldman

_Thomomys townsendii lenis_ Goldman, Proc. Biol. Soc.
Washington, 55:75, June 25, 1942.

_Thomomys perpallidus aureus_ Moore, Journ. Mamm., 10:259;
November 11, 1931.

_Type._--Male, adult, skin and skull, No. 264805, U. S. National Museum (Biological Surveys Collection); Richfield, 5,308 ft., Sevier County, Utah; March 11, 1928; collected by A. W. Moore; X-catalogue number 28835 (after Goldman, type not seen).

_Range._--Sevier River Valley from Piute County north to southwestern Juab and northeastern Millard counties, Utah.

_Diagnosis._--Size large (see measurements). Color: Upper parts Cinnamon Buff mixed with black in middorsal region; sides, flanks, forearms, thighs and underparts Pinkish Buff; inguinal region, front feet, hind feet, underpart of tail and end of tail white; postauricular patches small and dusky; chin, cheeks, nose and top of head dusky. Skull: Largest of Utah gophers, massive and angular; nasals long and denticulate distally; rostrum long and relatively narrow; zygomatic arches widely spreading and heavy throughout; jugals nearly vertical; zygomatic processes of maxillae heavy and flaring out abruptly from base of rostrum; union of zygomatic process of maxilla and jugal greatly thickened; extension of premaxillae posterior to nasals long; posterior tongues of premaxillae relatively narrow; lacrimal processes small; pterygoid hamulae long; interpterygoid space moderately V-shaped, tending to be somewhat lyre-shaped in some specimens; tympanic bullae somewhat flattened, only moderately inflated ventrally; upper incisors long and narrow; molariform teeth actually large, but relatively small.

_Comparisons._--Topotypes of _lenis_ can be distinguished from those of _Thomomys bottae tivius_, _convexus_, _contractus_, _albicaudatus_, _levidensis_, _centralis_ and _aureiventris_ by the following markedly greater average measurements of males: Total length, 250 mm.; length of nasals, 15.5; zygomatic breadth, 28.3; mastoid breadth, 22.5; and length of rostrum, 18.3. Other distinguishing characters are: Zygomatic arches more widely spreading; length of zygomatic processes of maxillae greater; and relatively longer, narrower rostrum.

_Remarks._--Twenty-one animals obtained from Lynndyl, Millard County, are all intergrades between _lenis_ and _aureiventris_. They are like _aureiventris_ in the shape of the zygomatic arches, and in the bowing of the parietal crests. Slight intergradation with _centralis_ is indicated by color and the shape of the nasals. The transverse arching of the posterior part of the rostrum is indicative of some relationship with _contractus_. In six other characters studied they most closely approach _lenis_ to which they are here referred.

Large size is the distinctive feature of _Thomomys bottae lenis_. The skulls are the largest of any species or subspecies of _Thomomys_ found in Utah. In total length, however, these animals are no longer than the extremes found in other named races. When Goldman (1942:75) described this race as new, he referred it to the species _Thomomys townsendii_, but remarked that the animal from Richfield was different enough from any other form then named to merit probably full specific status. I know of no character other than size to separate _Thomomys townsendii_ from _Thomomys bottae_, and since intergradation has been shown to exist between these alleged _townsendii_ from Richfield and animals from extreme western Utah known to belong to the species _bottae_, _lenis_ is here arranged as a subspecies of _Thomomys bottae_ which name has priority over _Geomys townsendii_.

The range here ascribed to this race is the Sevier River Valley from Piute County as far downstream as the town of Lynndyl which is near the eastern mainland of Pleistocene Lake Bonneville. The Sevier River continues farther out into Delta Valley ultimately to empty into Sevier Lake, which at present is adjacent to the area that formerly constituted the western mainland of the aforementioned ancient lake. This watercourse may have provided a migration route in ancient times, during the fluctuations of Lake Bonneville, whereby the animals formerly of the western mainland were able to come far eastward. The animals from Lynndyl which are intergrades between _lenis_, an eastern mainland form, and _centralis_ and _aureiventris_ which are western mainland forms of Lake Bonneville lend support to this hypothesis.

_Specimens examined._--Total, 26, distributed as follows:
_Millard County_: Lynndyl, 4,796 ft., 21. _Juab County_: U.
B. (= Yuba) Dam, 5,000 ft., 1. _Sevier County_: Salina,
4,575 ft., 1; Richfield, 5,308 ft., 3. (U. S. N. M.).

=Thomomys bottae levidensis= Goldman

_Thomomys bottae levidensis_ Goldman, Proc. Biol. Soc.
Washington, 55:76, June 25, 1942.

_Thomomys perpallidus aureus_ Bailey, N. Amer. Fauna, 39:75,
November 15, 1915; Barnes, Bull. Univ. Utah, 12 (No. 15):85,
April, 1922; Bull. Univ. Utah, 17 (No. 12):100, June, 1927.

_Type._--Male, adult, skin and skull, No. 191962, U. S. National Museum (Merriam Collection); Manti, 5,500 ft., Sanpete County, Utah; December 6, 1888; collected by Vernon Bailey; original number 427 (after Goldman, type not seen).

_Range._--San Pitch River Valley, Sanpete County, Utah.

_Diagnosis._--Size small (see measurements). Color: Upper parts and sides Cinnamon Buff, finely mixed with black along median line of back; underparts Pinkish Buff; nose, cheeks and chin grayish black; postauricular patches fairly large and grayish black; front and hind feet white (examples from type series badly stained); tail light buff but apparently white distally (the color of these specimens has apparently changed with age). Skull: Small, fairly robust; basilar length short; zygomatic arches weak, but widely spreading; tympanic bullae small; nasals short and simple distally; ventral margin of jugals convex dorsally; extension of premaxillae posterior to nasals relatively as well as actually long; posterior tongues of premaxillae relatively wide.

_Comparisons._--Topotypes of _levidensis_ differ from those of _Thomomys bottae absonus_ as follows: Size smaller. Color: Lighter throughout. Skull: Shorter, weaker and less ridged and angular, but relatively wider.

Compared with topotypes of _Thomomys bottae albicaudatus_, _levidensis_ differs as follows: Size smaller in every measurement taken. Color: Markedly lighter throughout. Skull: Smaller in every measurement taken; width relatively greater; skull smooth, weak and nonangular as opposed to ridged, robust and angular.

For comparisons with _Thomomys bottae lenis_ and _contractus_ see accounts of those forms.

_Remarks._--The range here ascribed to _levidensis_ is the San Pitch River Valley, which gradually merges southward into the Sevier River Valley. The latter valley in this area is inhabited by pocket gophers that belong to another subspecies, _lenis_. Nephi Valley to the west of San Pitch River Valley is inhabited by animals belonging to the subspecies _albicaudatus_. No known specimens show intergradation between _lenis_ and _levidensis_, but intergradation between _lenis_ and _albicaudatus_ is noted in the Nephi Valley animals (see account of _albicaudatus_). Superficially _levidensis_ resembles _absonus_ in size and color, but the skulls closely resemble those of _albicaudatus_, except for size in which they are smaller in all measurements. _T. b. albicaudatus_ is the most variable subspecies of _T. bottae_ occurring in Utah, and additional material from the Sevier River Valley between San Pitch River Valley and Nephi Valley may show _levidensis_ to be only a local variant of the highly variable subspecies, _albicaudatus_.

_Specimens examined._--Total, 6, from the type locality.

=Thomomys bottae osgoodi= Goldman

_Thomomys perpallidus osgoodi_ Goldman, Journ. Washington
Acad. Sci., 21:424, October 19, 1931.

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

_Thomomys perpallidus aureus_ Bailey, N. Amer. Fauna, 39:75,
November 15, 1915; Barnes, Bull. Univ. Utah, 12 (No. 15):85,
April, 1922; Bull. Univ. Utah, 17 (No. 12):100, June, 1927.

_Type._--Male, adult, skin and skull, No. 158530, U. S. National Museum (Biological Surveys Collection); Hanksville, Wayne County, Utah; October 20, 1908; collected by W. H. Osgood; original number 3701 (after Goldman, type not seen).

_Range._--Eastern Utah in the valleys of the drainage of the San Rafael, Dirty Devil and Price rivers.

_Diagnosis._--Size medium (see measurements). Color: Upper parts near (_e_) Pale Ochraceous Buff, definitely yellow in appearance; sides Pale Ochraceous Buff; entire underparts white, with a wash of Light Buff in the pectoral and inguinal regions; top of head, nose, cheeks, and chin dusky; postauricular patches grayish black; front feet, hind feet and distal part of tail white. Skull: Fairly robust but narrow; zygomatic arches concave medially in mid-jugal region; skull moderately convex dorsally, due to swelling in region of base of rostrum; lambdoidal suture situated well ahead of posterior margin of skull, with supraoccipital forming a side shelf at posterior part of skull; interpterygoid space narrowly V-shaped; tympanic bullae well inflated ventrally; basioccipital short; nasals rounded posteriorly; molariform teeth large.

_Comparisons._--Topotypes of _osgoodi_ differ from those of _Thomomys bottae absonus_ as follows: Size generally smaller. Color: Lighter throughout, more yellowish in appearance as opposed to buffy. Skull: Smaller in all measurements, except length of nasals, mastoid breadth, and alveolar length of upper molar series which are larger; rostrum shorter but relatively wider; zygomatic arches more robust and concave medially; palate wider; supraoccipital more bulging posteriorly; tympanic bullae more inflated ventrally; molariform teeth larger.

For comparisons with _Thomomys bottae aureus_ and _T. b. dissimilis_ see accounts of those forms.

_Remarks._--The animals here referred to _osgoodi_ are remarkably uniform in color, but vary widely in cranial details. Specimens from Carbon County are not typical and when more material becomes available it may prove that these animals from the northern part of the range of _osgoodi_ will merit separation and naming. The specimens from Emery County are not typical but resemble _osgoodi_ more than do the animals from Carbon County.

The range here ascribed to _osgoodi_ is in that part of the eastern Utah desert that is bounded on the east by the Green and Colorado rivers, on the west by the high mountains of central Utah, on the north by the Book Cliffs and on the south by the Dirty Devil River. This area is an uninviting wasteland in which there are relatively few roads and little water. In addition, it is greatly cut up by washes and gullies which contain water only during a few weeks of the year. The continuation of this area of wasteland southward beyond the Dirty Devil River is inhabited by pocket gophers belonging to the subspecies _absonus_. If specimens were available they would undoubtedly show intergradation to exist between _osgoodi_ and _absonus_.

_Specimens examined._--Total, 14, distributed as follows:
_Carbon County_: 1-2 mi. N Spring Glen, 6,150 ft., 2; Spring
Glen, 6,200 ft., 2; 2 mi. E Spring Glen, 6,200 ft., 1.
_Emery County_: Price River, 2 mi. SE Woodside, 4,600 ft., 2
(C. M.); Green River, 4,080 ft., 5 (M. V. Z.). _Wayne
County_: Hanksville, 2 (U. S. N. M.).

=Thomomys bottae howelli= Goldman

_Thomomys bottae howelli_ Goldman, Journ. Washington Acad.
Sci., 26:116, March 15, 1936.

_Type._--Female, adult, skin and skull, No. 25684, U. S. National Museum (Biological Surveys Collection); Grand Junction, 4,600 ft., Mesa County, Colorado; November 7, 1895; collected by A. H. Howell; original number 493 (after Goldman, type not seen).

_Range._--In the valleys of eastern Utah, east of the Green River and north of the Colorado River.

_Diagnosis and Comparisons._--Inasmuch as there is but one specimen, the holotype known, and as it was impossible to study it, the following diagnoses and comparisons are from Goldman, (1936:116).

"_General characters._--A rather large, pallid subspecies with a broad, flattened cranium. Similar to the palest specimens of _Thomomys bottae aureus_ of the San Juan River Valley, southeastern Utah, in color, but underparts more thinly overlaid with buffy white, and cranial characters, especially the broad, flat braincase, distinctive. Approaching _Thomomys bottae osgoodi_ of the Fremont River Valley, Utah, in color, but much larger and skull widely different.

"_Color._--Type (winter pelage): Upper parts in general between tilleul buff and pale olive buff (Ridgway 1912), somewhat darkened on head by a mixture of cinnamon buff and brown; a few inconspicuous dusky-tipped hairs along median line of back; muzzle dusky; ears and postauricular spots deep, contrasting black; underparts thinly overlaid with buffy white, the hairs becoming pure white to roots on inguinal region; thighs pure white to roots all around; feet white; tail buffy whitish, slightly paler below than above.

"_Skull._--Similar in general to that of _T. b. aureus_, but braincase conspicuously broader and flatter; zygomata more widely spreading; nasals shorter; premaxillae more attenuate posteriorly; interparietal larger; audital bullae more rounded and fully inflated anteriorly; incisors short, as in _aureus_, but less strongly recurved. Compared with that of _T. b. osgoodi_ the skull is much larger, with flatter braincase, shorter nasals, and posteriorly narrower premaxillae."

_Remarks._--Six specimens, in the Carnegie Museum from 10 miles north of Moab, Grand County, Utah, were available for this study. They are not typical of _howelli_ as it is diagnosed by Goldman (_loc. cit._). They appear to be intergrades between _howelli_ and _osgoodi_ in cranial characters, but more closely resemble _howelli_, particularly in the flat, widened, low braincase. In color, some specimens seem to intergrade toward _aureus_.

The range ascribed to this form in Utah appears to be one of the most natural ones within the state since it is bounded by the Green and Colorado rivers which have formed deep rocky gorges in this region.

_Specimens examined._--Total, 6, as follows: _Grand County_:
10 mi. N Moab, 6 (C. M.).

=Thomomys bottae wahwahensis= Durrant

_Thomomys bottae wahwahensis_ Durrant, Bull. Univ. Utah, 28
(No. 4):4, August 18, 1937.

_Type._--Male, adult, skin and skull, No. 1750, Museum of Zooelogy, University of Utah, Wah Wah Springs, 30 mi. W Milford, 6,500 ft., Beaver County, Utah; July 22, 1936; collected by S. D. Durrant; original number 989.

_Range._--Westcentral Utah, in Wah Wah Mountains, and Pine Valley to the west of these mountains.

_Diagnosis._--Size medium (see measurements). Color: Upper parts Pinkish Buff; underparts Pale Pinkish Buff with considerable admixture of gray; inguinal and pectoral regions Pale Pinkish Buff; nose and cheeks grayish black; postauricular patches small and black; front feet, hind feet and distal one-third to one-half of tail white. Skull: Flat dorsoventrally; rostrum short and wide; premaxillae broad and heavy; nasals short and straight, with no arching as viewed laterally; tympanic bullae small; space enclosed within zygomatic arches short antero-posteriorly; alveolar length of upper molar series short; molariform teeth small.

_Comparisons._--From topotypes of _Thomomys bottae centralis_, _wahwahensis_ differs as follows: Size smaller in every measurement taken. Color: Lighter, Pinkish Buff as opposed to Cinnamon Buff. Skull: Rostrum wider, shorter and more nearly flat; nasals straight as opposed to moderately convex; tympanic bullae smaller and less inflated ventrally; zygomatic arches more widely spreading and angular; molariform teeth smaller; extension of premaxillae posterior to nasals less.

From topotypes of _Thomomys bottae albicaudatus_, _wahwahensis_ differs as follows: Hind foot shorter. Color: Lighter throughout, Pinkish Buff as opposed to (13''''_n_) Black. Skull: Smaller and more nearly flat; rostrum shorter, wider and more nearly flat; nasals straight as opposed to convex; zygomatic breadth less but mastoid breadth greater; tympanic bullae smaller, and less inflated ventrally; extension of premaxillae posterior to nasals less; molariform teeth smaller.

From topotypes of _Thomomys bottae aureiventris_, _wahwahensis_ differs in the following features: Size smaller; hind foot shorter. Color: Lighter throughout, no "gold" on underparts. Skull: Smaller in nearly every measurement taken; rostrum shorter and relatively wider; zygomatic arches more angular and relatively more widely spreading; nasals shorter and more nearly flat; thickening at union of jugal and zygomatic process of maxilla less; interpterygoid space V-shaped as opposed to lyre-shaped; tympanic bullae much smaller, and less inflated ventrally; molariform teeth much smaller.

Topotypes of _wahwahensis_ can be easily distinguished from those of _Thomomys bottae tivius_ by their markedly larger size in every measurement taken, lighter color, and larger, more robust and more nearly flat skull.

For comparisons of _wahwahensis_ with _Thomomys bottae sevieri_, _robustus_, _bonnevillei_ and _convexus_ see comparisons under those forms.

Among the named races of _Thomomys bottae_, _wahwahensis_ definitely has its affinities with _planirostris_ from Zion National Park. Both possess flat skulls with wide, short rostra. It differs from the latter in: Size smaller in every measurement taken. Color: Lighter throughout. Skulls: Nasals and rostrum shorter and more nearly flat; tympanic bullae markedly smaller; alveolar length of upper molar series shorter; molariform teeth markedly smaller and weaker.

_Remarks._--Wah Wah Springs, the type locality of _wahwahensis_, are on the summit of a low pass in the Wah Wah Mountains in the desert of west central Utah. The surrounding valleys, for many miles, as far as my investigations show, are not inhabited by pocket gophers, except the Desert Range Experiment Station of the United States Forest Service in Pine Valley to the west of these mountains. There, pocket gophers were obtained which are intergrades between _centralis_ and _wahwahensis_. In five out of seven characters investigated these gophers resemble _wahwahensis_, to which they are here referred. Study of the topography reveals the probable means by which the animals reached this valley. The long axis of the Wah Wah Mountains is north and south, but a westward arm forms the northern boundary of Pine Valley. Around springs in this westward projecting arm workings of pocket gophers were found. With the development of water at the Desert Range Experiment Station, and subsequent improvement of forage, these animals probably came down into the valley from the springs to the north.

The terrain between the Desert Range Experiment Station in Pine Valley and Snake Creek (where _centralis_ occurs) to the west is not inhabited by pocket gophers at present. This area, however, forms part of the southwest mainland of Pleistocene Lake Bonneville, which mainland in times past was probably suitable for pocket gophers. Since the close of the Pleistocene, aridity has rendered most of it unfit for pocket gophers, and they remain only in isolated areas where suitable environments still persist.

_Specimens examined._--Total, 18, distributed as follows:
_Millard County_: Desert Range Experiment Station, United
States Forest Service, Sec. 9, T. 25 S, R. 17 W, Salt Lake
Base Meridian, 6. _Beaver County_: Wah Wah Springs, Wah Wah
Mountains, 30 mi. W Milford, 6,500 ft., 12 (2, M. V. Z.).

=Thomomys bottae dissimilis= Goldman

_Thomomys perpallidus dissimilis_ Goldman, Journ. Washington
Acad. Sci., 21:425, October 19, 1931.

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

_Thomomys perpallidus aureus_ Bailey, N. Amer. Fauna 39:75,
November 15, 1915; Barnes, Bull. Univ. Utah, 12 (No. 15):85,
April, 1922; Bull. Univ. Utah, 17 (No. 12):100, June, 1927.

_Type._--Female, adult, skin and skull, No. 158526, U. S. National Museum (Biological Surveys Collection); E slope Mount Ellen, Henry Mountains, 8,000 ft., Garfield County, Utah; October 15, 1908; collected by W. H. Osgood; original number 3677 (after Goldman, type not seen).

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

_Diagnosis._--Size small (see measurements). Color: Upper parts Light Buff, grading over sides to nearly white on underparts; underparts lightly washed with Pale Buff, more marked in inguinal and pectoral regions; postauricular patches grayish black; nose, chin, cheeks and top of head dusky; front feet, hind feet and distal half of tail white. Skull: Small and weak; zygomatic arches long, but lying close to skull, giving it a slender appearance; supraoccipital markedly projecting posteriorly from lambdoidal suture; rostrum relatively long and narrow; nasals long; tympanic bullae well inflated ventrally, with a median ventral ridge; pterygoid hamulae weak; interpterygoid space narrowly V-shaped; upper incisors short and light in color; molariform teeth relatively large.

_Comparisons._--Comparison of one topotype of _dissimilis_ with topotypes of _Thomomys bottae aureus_ shows it to differ as follows: Size smaller throughout. Color: Lighter dorsally and on sides, pale buff as contrasted with rich ochraceous; underparts more buffy. Skull: Smaller in every measurement taken; zygomatic arches markedly less widely spreading; braincase narrower and more vaulted; tympanic bullae with a median ventral ridge as opposed to smooth; pterygoid hamulae slenderer; interpterygoid space narrowly V-shaped as opposed to U-shaped; upper incisors smaller and lighter in color.

Compared with topotypes of _Thomomys bottae absonus_, _dissimilis_ differs in the following features: Size smaller in every measurement taken. Color: Lighter throughout. Skull: Smaller in every measurement taken, except alveolar length of upper molar series which is greater; skull narrower and weaker; zygomatic arches weaker and less widely spreading; tympanic bullae more ridged on ventral surface and shorter (more rounded) in antero-posterior measurement; upper incisors shorter and narrower; molariform teeth larger.

_Thomomys bottae dissimilis_ resembles _T. b. osgoodi_ more than any other subspecies but differs in: Size smaller throughout. Color: Slightly darker dorsally. Skull: Smaller in every measurement taken, and slenderer; rostrum relatively longer; zygomatic arches weaker, and less widely spreading, more converging anteriorly; tympanic bullae less rounded, more ridged medioventrally; upper incisors shorter but narrower; molariform teeth smaller.

_Remarks._--The Henry Mountains, in eastern Garfield County, are in the Colorado River drainage. The surrounding country is desertlike and cut by gullies and washes with sheer escarpments and precipitous draws. The type locality of _dissimilis_ is possibly in an isolated area. Only three specimens were available to Goldman when he named _dissimilis_. He commented on the close resemblance to _osgoodi_ which inhabits the country to the north. I have examined only one of the three specimens available to Goldman. Although I can see the characters that he mentioned, I am not fully convinced that _dissimilis_ is separable from _osgoodi_. Two specimens from Escalante, Garfield County, are referred to _absonus_, but they show intergradation with _dissimilis_.

_Specimens examined._--One (U. S. N. M.) from E slope Mount
Ellen, Henry Mountains, 8,000 ft., Garfield County.

=Thomomys bottae aureus= Allen

_Thomomys aureus_ Allen, Bull. Amer. Mus. Nat. Hist., 5:49,
April 28, 1893.

_Thomomys bottae aureus_ Goldman, Proc. Biol. Soc.
Washington, 48:156, October 31, 1935; Benson, Univ.
California Publ. Zooel., 40:450, December 31, 1935.

_Thomomys fulvus aureus_ Goldman, Journ. Washington Acad.
Sci., 21:417, October 19, 1931; Journ. Washington Acad.
Sci., 23:464, October 15, 1933.

_Thomomys perpallidus aureus_ Bailey, N. Amer. Fauna, 39:74,
November 15, 1915; Barnes, Bull. Univ. Utah, 12 (No. 15):85,
April, 1922; Bull. Univ. Utah, 17 (No. 12):100, June, 1927.

_Type._--No. 5243/4123. American Museum of Natural History; Bluff City, San Juan County, Utah; May 12, 1892; collected by Charles P. Rowley (after Allen, type not seen).

_Range._--All of San Juan County (except extreme southwestern part) and Grand County east of the Colorado River.

_Diagnosis._--Size large (see measurements). Color: Upper parts Cinnamon Buff, lighter on sides; underparts generally white, or if colored at all with only a faint wash of Light Buff; nose and chin blackish gray; top of head blackish due to admixture of black hairs; postauricular patches small and dusky; front feet and hind feet white. Skull: Long, narrow but massive; zygomatic arches not widely spreading, but heavy; jugals thick, union of jugals and zygomatic processes of maxillae thickened; rostrum long but wide; top of rostrum convex in lateral view; ascending processes of premaxillae wide and heavy; nasals thin proximally; braincase long and narrow; tympanic bullae well inflated ventrally; alveolar length of upper molar series long; molars large; pterygoid hamulae heavy; interpterygoid space U-shaped; palate arched; upper incisors long and wide.

_Comparisons._--Compared with topotypes of _Thomomys bottae osgoodi_, _aureus_ differs as follows: Size larger in every measurement taken, except tail which is shorter. Color: Darker throughout except on ventral surface which is lighter. Skull: Larger, longer and wider; nasals longer; rostrum wider and longer; zygomatic arches more nearly straight and heavier; ascending processes of premaxillae wider; basioccipital longer; interpterygoid space U-shaped as opposed to V-shaped; tympanic bullae larger; upper incisors longer, wider; molars larger.

Topotypical specimens of _aureus_ can be distinguished from those of _Thomomys bottae dissimilis_ by: Size larger throughout. Color: A trifle darker on dorsal surface. Skull: Larger in every measurement taken; zygomatic arches heavier and more nearly straight; tympanic bullae larger and more inflated ventrally; interpterygoid space U-shaped as opposed to V-shaped; alveolar length of upper molar series longer; molars larger; upper incisors longer and wider.

Topotypes of _aureus_ differ from those of _Thomomys bottae absonus_ as follows: Size larger in every measurement taken. Color: Darker dorsally, Light Ochraceous as opposed to Cinnamon Buff; due to admixture of gray, _absonus_ has more of a grayish cast. Skull: Larger in every measurement taken, longer, narrower and more compact; zygomatic arches heavier; ascending processes of premaxillae wider; jugals heavier; tympanic bullae larger; interpterygoid space U-shaped rather than V-shaped; upper incisors longer and wider; molars larger.

From topotypes of _Thomomys bottae planirostris_, _aureus_ can be distinguished as follows: Size larger; tail shorter. Color: Lighter throughout. Skull: Larger in every measurement taken except zygomatic breadth, extension of premaxillae posterior to nasals, and length of upper molariform series which are less; rostrum longer, wider and more convex; nasals slightly arched rather than straight; depression absent rather than present in posterior region of nasals; zygomatic arches not so widely spreading, but equally heavy.

For comparisons with _Thomomys bottae alexandrae_, see accounts under that form.

_Remarks._--Topotypes of _aureus_ are among the largest pocket gophers in the state. They are exceeded in total length only by _T. b. lenis_ and are approached by _T. b. aureiventris_ and _T. b. planirostris_. On the average they have the longest hind foot, body and ear. The length of the skull is second only to that of _lenis_ as also is the length and breadth of the rostrum relative to the basilar length.

From the time of the original description of _aureus_ in 1893 until 1930, all light colored gophers from Utah were referred to that form. Barnes (1927:100) gives the range of _aureus_ as extending completely across southern Utah and on the west and east sides as far north as central Utah. Since 1930, forms named by E. R. Hall, W. H. Burt, E. A. Goldman and the writer have restricted the range of _aureus_ in Utah to that part of the state east of the Colorado River.

_Specimens examined._--Total, 22, as follows: _San Juan
County_: Bluff, 3,300 ft., 22 (15, M. V. Z.).

=Thomomys bottae birdseyei= Goldman

_Thomomys bottae birdseyei_ Goldman. Proc. Biol. Soc.
Washington, 50:134, September 10, 1937.

_Thomomys perpallidus aureus_ Bailey, N. Amer. Fauna, 39:75,
November 15, 1915; Barnes, Bull. Univ. Utah, 12 (No. 15):85,
April, 1922; Bull. Univ. Utah, 17 (No. 12):100, June, 1927.

_Type._--Male, adult skin and skull, No. 161654. U. S. National Museum (Biological Surveys Collection); Pine Valley Mountains, 5 mi. E Pine Valley, 8,300 ft., Washington County, Utah; April 10, 1909; collected by Clarence Birdseye; original number 861 (after Goldman, type not seen).

_Range._--High mountains and plateaus of southwestern Utah.

_Diagnosis._--Size medium (see measurements). Color: Upper parts between Cinnamon and Sayal Brown, finely mixed with black in median dorsal region, grading over sides and flanks to Cinnamon on underparts; front feet, hind feet, and distal part of tail white; postauricular patches, chin, cheeks and top of head grayish black. Skull: Depressed along median line of frontals and posterior ends of nasals; region of nasofrontal suture concave ventrally; zygomatic arches heavy and widely spreading, widest posteriorly; posterior ends of nasals straight, tending to be somewhat rounded in some specimens; extension of premaxillae posterior to nasals moderate; tympanic bullae moderately inflated ventrally; basioccipital wide; interpterygoid space widely V-shaped.

_Comparisons._--Topotypes of _birdseyei_ differ from near topotypes of _Thomomys bottae virgineus_, from Beaverdam Wash as follows: Size larger; tail and hind foot longer. Color: Darker throughout, between Cinnamon and Sayal Brown as opposed to Cinnamon Buff. Skull: Larger in every measurement taken except extension of premaxillae posterior to nasals, and length and width of rostrum which are less; skull more depressed in nasofrontal region; zygomatic arches more widely spreading; zygomatic processes of squamosals shorter; pterygoid hamulae longer; tympanic bullae smaller and less inflated ventrally.

Among named races of _T. bottae_, _birdseyei_ most closely resembles _trumbullensis_ in size, but differs as follows: Hind foot and tail longer. Color: Lighter throughout; postauricular patches smaller and lighter. Skull: Larger; mastoid breadth less; zygomatic arches wider and more widely spreading posteriorly; median frontal depression more marked; extension of premaxillae posterior to nasals greater; tympanic bullae less inflated ventrally; molariform teeth larger.

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

_Remarks._--_T. b. birdseyei_ is apparently endemic to the mountainous area of southwestern Utah in Washington and Iron counties. It intergrades with _virgineus_ and with _planirostris_ as described in the account of the latter.

_Specimens examined._--Total, 8, distributed as follows:
_Washington County_: Pine Valley, 1 (U. S. N. M.); Pine
Valley Mountains, 5 mi. E Pine Valley, 8,300 ft., 3 (U. S.
N. M.); Pine Valley campground, 6,800 ft., 1 (R. H.); 3/4
mi. E town of Pine Valley, 6,500 ft., 3 (R. H.).

_Additional records._--_Washington County_: Hebron, 1;
Mountain Meadows, 2 (Bailey 1915:75).

=Thomomys bottae virgineus= Goldman

_Thomomys bottae virgineus_ Goldman, Proc. Biol. Soc.
Washington, 50:133, September 10, 1937.

_Type._--Male, adult, skin and skull, No. 262016, U. S. National Museum (Biological Surveys Collection); Beaverdam Creek, near confluence with Virgin River, Littlefield, 1,500 ft., Mohave County, Arizona; October 16, 1936; collected by Luther C. Goldman; original number 67 (after Goldman, type not seen).

_Range._--Extreme southwestern Utah, in Beaverdam Wash, Washington County, Utah.

_Diagnosis._--Size medium (see measurements). Color: Upper parts Cinnamon Buff, finely mixed with black; sides and flanks Pinkish Buff; underparts Pale Pinkish Buff; front feet, hind feet, and distal part of tail white; nose, cheeks, chin and top of head grayish black. Skull: Robust, with moderately wide zygomatic arches; zygomatic processes of maxillae wide; zygomatic processes of squamosals long; jugals concave laterally, giving the zygomatic arches the appearance of double bowing; nasals long; extension of premaxillae posterior to nasals long; tympanic bullae well inflated ventrally; pterygoid hamulae heavy; interpterygoid space widely V-shaped; molariform teeth large.

_Comparisons._--For comparisons of _virgineus_ with _Thomomys bottae planirostris_ and _T. b. birdseyei_ see accounts under those forms.

Topotypical specimens of _virgineus_ can be distinguished from those of _Thomomys bottae trumbullensis_ as follows: Size smaller. Color: Lighter throughout. Skull: Zygomatic arches less widely spreading; jugals more bowed medially; zygomatic processes of squamosals longer; extension of premaxillae posterior to nasals greater; tympanic bullae larger and more inflated ventrally; molariform teeth larger.

Compared with topotypes of _Thomomys bottae centralis_, _virgineus_ differs in: Size smaller; tail shorter; hind foot smaller. Color: Deeper Cinnamon Buff, thus darker in overall appearance. Skull: Smaller, but relatively wider; zygomatic processes of maxillae heavier; region of maxillo-jugal sutures thicker; jugals more concave laterally; tympanic bullae more inflated ventrally; molariform teeth larger.

_Remarks._--This pocket gopher occupies practically the same range in Utah as the large kangaroo rat _Dipodomys deserti deserti_ Stephens. Both are found in the Beaverdam Wash. The type locality of _virgineus_ is but a short distance down the Beaverdam Creek at Littlefield, Arizona. It intergrades with _birdseyei_, the mountain form to the north and east (see remarks under _birdseyei_). There are evidences of intergradation with _planirostris_ of the Virgin River Valley above the narrows of the Virgin River where it cuts through the Beaverdam Mountains (see the discussion under _planirostris_). There are intergradational tendencies exhibited towards _centralis_ in some specimens. Some of the animals are practically indistinguishable in color and there are intergrading cranial characters in the nasals, zygomatic arches and tympanic bullae.

_Specimens examined._--Total, 20, distributed as follows:
_Washington County_: Beaverdam Wash, 8 mi. N Utah-Arizona
border, 7; Beaverdam Wash, 5 mi. N Utah-Arizona border,
2,600 ft., 13.

=Thomomys bottae planirostris= Burt

_Thomomys perpallidus planirostris_ Burt, Proc. Biol. Soc.
Washington, 44:38, May 8, 1931.

_Thomomys bottae planirostris_ Hall and Davis, Proc. Biol.
Soc. Washington, 47:52, February 9, 1934; Goldman, Proc.
Biol. Soc. Washington, 48:156, October 31, 1935; Presnall,
Zion-Bryce Mus. Bull., 2:14, January, 1938; Long, Journ.
Mamm., 21:176, May 14, 1940.

_Thomomys perpallidus aureus_ Bailey, N. Amer. Fauna, 39:75,
November 15, 1915; Barnes, Bull. Univ. Utah, 12 (No. 15):85,
April, 1922; Bull. Univ. Utah, 17 (No. 12):100, June, 1927;
Woodbury, Ecological Monographs, 3:193, April, 1933.

_Thomomys bottae centralis_ Hall and Davis, Proc. Biol. Soc.
Washington, 47:52, February 9, 1934; Presnall, Zion-Bryce
Mus. Bull., 2:14, January, 1938.

_Thomomys perpallidus centralis_ Hall, Univ. California
Publ. Zooel., 23:445, July 8, 1930.

_Thomomys bottae nicholi_ Goldman, Journ. Washington Acad.
Sci., 28:337, July 15, 1938, type from Shivwits Plateau, 20
mi. S Wolf Hole (road to Parashonts), 5,000 ft., Mohave
County, Arizona; Hardy, Ecological Monographs, 15:98,
January, 1945.

_Thomomys bottae trumbullensis_ Hall and Davis, Proc. Biol.
Soc. Washington, 47:52, February 9, 1934.

_Type._--Male, adult, skin and skull, No. 8395, Collection of Donald R. Dickey; Zion National Park, Washington County, Utah; May 4, 1920; collected by A. Brazier Howell; original number 2184 (after Burt, type not seen).

_Range._--Valley of the Virgin River from Zion National Park west to the Beaverdam Mountains.

_Diagnosis._--Size large (see measurements); tail long. Color: Upper parts Sayal Brown; underparts between Vinaceous Cinnamon and Cinnamon, grading to Pinkish Cinnamon in some specimens; nose, chin, cheeks, postauricular patches, and top of head grayish black; front feet and hind feet white; tail Pinkish Buff, with distal third white. Skull: Massive and ridged; nasals straight and flat, simple distally; dorsal surface of rostrum slightly concave at proximal end of nasals; zygomatic arches widely spreading, widest posteriorly; zygomatic processes of maxillae heavy; premaxillae broad and extending far beyond posterior end of nasals; rostrum wide and heavy; palate slightly arched; pterygoid hamulae heavy; interpterygoid space V-shaped; tympanic bullae moderately inflated ventrally, somewhat compressed laterally; upper incisors long and heavy; molariform teeth large.

_Comparisons._--Compared with topotypes of _Thomomys bottae birdseyei_, _planirostris_ differs as follows: Size larger, except total length which averages slightly less in females. Color: Lighter throughout. Skull: Larger in every measurement taken; more massive; rostrum wider, longer and more nearly flat; nasals straight and not inflated dorsally on distal end; premaxillae wider at posterior ends; extension of premaxillae posterior to nasals greater; zygomatic arches heavier, especially the zygomatic processes of the maxillae; posterior ends of nasals more nearly truncate as opposed to generally rounded; tympanic bullae more nearly flat and relatively smaller; upper incisors longer and heavier; interpterygoid space more narrowly V-shaped; molariform teeth much heavier.

Topotypes of _planirostris_ differ from near topotypes of _Thomomys bottae virgineus_ as follows: Size larger; tail and hind foot longer. Color: Slightly darker dorsally, but markedly darker ventrally; postauricular patches smaller and lighter. Skull: Larger in every measurement taken; skull more massive; nasals flat, neither arched nor swollen distally; rostrum wider; nasofrontal region flattened or concave as opposed to convex; premaxillae relatively narrower; zygomatic arches heavier, especially in the processes of the maxillae; tympanic bullae smaller and less inflated ventrally; interpterygoid space generally more narrowly V-shaped; upper incisors longer and heavier; molariform teeth larger.

From topotypes of _Thomomys bottae trumbullensis_, _planirostris_ differs in: Size larger throughout; tail longer. Color: Much lighter throughout. Skull: More convex dorsally; rostrum wider and more depressed distally; extension of premaxillae posterior to nasals greater; zygomatic arches shorter, and not as widely spreading posteriorly; interpterygoid space more narrowly V-shaped; tympanic bullae smaller; upper incisors wider and longer; molariform teeth larger.

Topotypes of _planirostris_ can be easily distinguished from those of _Thomomys bottae absonus_ by darker color throughout and markedly larger size.

_Remarks._--From the synonomy at the beginning of this account one may note that the animals here ascribed to this subspecies have had nearly as many subspecific names applied to them as there have been investigators who have written about them. Although each of the previous writers had but a small amount of material upon which to base his opinion, the diversity of opinion as to subspecific status bespeaks the instability of these animals. The present study is based upon eighty animals including additional comparative material.

All animals from Zion National Park have the characters pointed out by Burt (1931:38) in his description of this form. Farther down the Virgin River Valley towards St. George, however, some very perplexing problems of intergradation are encountered. St. George and environs may correctly be thought of as a "melting pot." Each of the fifty-seven animals studied from this region is an intergrade; some specimens combine the characters of three subspecies.

As may be seen on the distribution map, three different subspecies of _Thomomys bottae_ occur in Washington County. Down the river, below St. George, the race _virgineus_ inhabits the Virgin River Valley below the narrows of the Beaverdam Mountains. Because these narrows are filled with water from wall to wall during periods of high runoff, they form an effective barrier at present to migration of pocket gophers. The mountains to the north of St. George are inhabited by the dark form, _birdseyei_. The type locality of _planirostris_ is on the middle reaches of the Virgin River, in Zion National Park. In addition Mount Trumbull to the south, in northern Arizona, is the locality of another subspecies, _trumbullensis_.