The Pocket Gophers (Genus Thomomys) of Utah / University of Kansas Publications, Museum of Natural History, Vol. 1 No. 1

Thomomys bottae sevieri new subspecies

Type.—Female, adult, skin and skull, No. 2530, Museum of Zoölogy, 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.

Thomomys bottae convexus Durrant

Type.—Male, adult, skin and skull, No. 2482, Museum of Zoölogy, 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.

Thomomys bottae tivius Durrant

Type.—Female, adult, skin and skull, No. 1827, Museum of Zoölogy, 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 Cañon 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 Cañon 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.

Thomomys bottae contractus new subspecies

Type.—Male, adult, skin and skull, No. 1851, Museum of Zoölogy, 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 Cañon 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.

Thomomys bottae lenis Goldman

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.

Thomomys bottae levidensis Goldman

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.

Thomomys bottae osgoodi Goldman

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.

Thomomys bottae howelli Goldman

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.

Thomomys bottae wahwahensis Durrant

Type.—Male, adult, skin and skull, No. 1750, Museum of Zoölogy, 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.

Thomomys bottae dissimilis Goldman

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.