white. Skull: Long and slender, but relatively wide across mastoidal region; nasals long and rounded posteriorly; rostrum long and narrow; zygomatic arches weak and not widely spreading, tending to be slightly bowed out posteriorly, but in the main roughly parallel to the sides of the skull; outer margin of zygomatic arch slightly concave, and zygomatic arch dips deeply ventrad; dorsal surface of skull smooth, with weakly defined parietal crests; parietal crest nearly parallel, but bowed medially, in parietal region, and flaring widely posteriorly to pass lateral to interparietal; tympanic bullae large, truncate anteriorly and markedly inflated ventrally; upper incisors short and fairly robust.

Comparisons.—From Thomomys talpoides uinta, oquirrhensis may be differentiated as follows: Color: Darker throughout; postauricular patches larger and darker; ears longer and more pointed; inner margin of pinna heavily pigmented; external opening of ear smaller. Skull: Nasals rounded posteriorly rather than deeply emarginate, and less flaring distally; zygomatic arches weaker and markedly less widely spreading; pterygoid hamulae weaker; basisphenoid narrower; upper incisors shorter and wider.

For comparisons between oquirrhensis and Thomomys talpoides gracilis, and oquirrhensis and wasatchensis, see comparisons under those forms.

Topotypical specimens of oquirrhensis can be distinguished from those of Thomomys talpoides moorei as follows: Color generally darker, due to greater admixture of black; terminal bands of hair actually lighter; postauricular patches larger and darker; ears longer, more pointed and with more heavily pigmented pinnae; tail shorter. Skull: About the same size; smoother; zygomatic arches weaker and less widely spreading; nasals rounded posteriorly as opposed to emarginate; mastoid breadth less; pterygoid hamulae weaker; upper incisors wider.

Remarks.—This race is limited to the Oquirrh Mountains, a high mountain range that lies parallel to, and just west of the Wasatch Mountains, in Utah, Salt Lake and Tooele counties. These mountains were connected in past times to the Wasatch Mountains by the Transverse Range, and by a sand and gravel bar deposited by Pleistocene Lake Bonneville. The Jordan River in its course from Utah Lake to the Great Salt Lake has cut a channel through the aforementioned bar. This channel has been cut to the level of the surrounding valleys as is indicated by the meandering nature of the stream through this part of its course. As a result the Oquirrh Mountains are relatively isolated. Although separated from the Wasatch Mountains by the Jordan River Valley only a few miles wide, the pocket gophers are distinct on each mountain. A population of T. bottae is interposed between the two mountain ranges as is indicated by specimens from Riverton, six miles north of the Transverse Range. The populations of bottae are subspecifically the same on the two sides of the Jordan River.

On the east side of the Oquirrh Mountains, pocket gophers collected from the Jordan Valley up Rose Canyon to about 5,000 feet elevation were all of the species T. bottae. Between 5,000 and 6,000 feet there is an area in which the ranges of bottae and talpoides overlap. When trapping, it is possible to predict what species will be taken by the types of burrows and soil. Gophers of the bottae group have their burrows in the areas of the deepest soil and heaviest vegetation, whereas the areas of shallow, rocky soil covered with sparse vegetation are the habitat of talpoides. Above 6,000 feet the only gopher encountered is talpoides. Along Settlement Creek on the west side of the Oquirrh Mountains, which is the type locality of oquirrhensis, bottae and talpoides have essentially the same vertical distribution as in Rose Canyon. On this mountain the two species appear to be in competition.

The available information, based on collections, indicates that the Oquirrh Mountains are the only mountains west of the Wasatch Range upon which talpoides occurs. In Utah, all other mountains to the west, as far as known, are inhabited by subspecies of of Thomomys bottae.

Thomomys talpoides uinta Merriam

Type.—Male, adult, skin and skull, No. 22501/30051, U. S. National Museum (Biological Surveys Collection); north base Gilbert Peak, Uinta Mountains, 10,000 ft., Summit County, Utah; June 6, 1890; collected by Vernon Bailey; original number 1262 (after Merriam, type not seen).

Range.—Uinta Mountains in Duchesne County, eastern Wasatch and Summit counties, and western Uintah County south to the Roan, Brown and Book cliffs in Carbon County.

Diagnosis.—Size medium (see measurements). Color: Upper parts Snuff Brown finely mixed with black, paling over sides and flanks to near Pinkish Buff on underparts; postauricular patches relatively small and dusky; external opening of ear large; pinnae usually lightly pigmented; hind feet white; front feet usually white only at base of toes; distal third to half of tail white; tail usually light below, with proximal dorsal half covered with darker hairs; nose, chin, cheeks and top of head dusky; usually considerable white on throat. Skull: Small, slender, and not heavily ridged; nasals short and dilated distally; posterior margins of nasals emarginate; zygomatic arches moderately widely spreading, widest posteriorly; interparietal pentagonal or subquadrangular; interpterygoid space V-shaped; tympanic bullae well inflated ventrally; upper incisors long and narrow.

Comparisons.—For comparisons with other subspecies of Thomomys talpoides, see accounts of those forms.

Remarks.—The range formerly ascribed to uinta (Bailey, 1915:114; Barnes, 1922:83, 1927:104) is now known to be inhabited by animals belonging to three distinct subspecies. The range of uinta as now understood is restricted to the southern and western parts of the Uinta Mountains and their environs. Three specimens from the Book Cliffs, Sunnyside, Carbon County, are not typical, but in a majority of their characters agree with uinta to which they are here referred.

I have seen only one specimen from the type locality. It is one of the series on which Merriam (1901:112) based his original description. In addition, I have studied several large series of near topotypes. From the material at hand, and from Merriam's description (loc. cit.), I regard the animals on which the name uinta was based as intergrades between Thomomys talpoides ravus, the race to the northeast, on the one hand and the animals of the western and southern parts of the Uinta Mountains on the other hand. The affinities of the type series are with the animals from the latter area which are here all referred to