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.