Topotypes of ocius can be distinguished from those of _Thomomys talpoides uinta_ as follows: Color: Lighter throughout, grayish as opposed to brown. Skull: Nasals rounded posteriorly as opposed to emarginate; zygomatic arches more robust; interparietal pentagonal as opposed to subquadrangular; extension of supraoccipital posterior to lambdoidal suture markedly greater; tympanic bullae actually as well as relatively much larger; upper incisors short and strongly recurved as opposed to long and procumbent. Specimens of this subspecies can be distinguished from all other members of the species _Thomomys talpoides_ occurring in Utah by their grayish color, and by small, compact skulls with very large tympanic bullae and short strongly recurved upper incisors. _Remarks._--Two specimens from Vernal, Uintah County, are intergrades between _ocius_ and _uinta_. They resemble _uinta_ in size and dorsal color, but are slightly lighter tending toward the color of _ocius_. Ventrally they are intermediate in color but more like _ocius_. The skulls are more like those of _ocius_ in general appearance, extension of supraoccipital posterior to the lambdoidal suture, shape and thickness of the zygomatic arches, posterior tongues of premaxillae, size of tympanic bullae and recurved upper incisors. They more closely resemble _uinta_ in shape of posterior ends of nasals, basioccipital and shape of the zygomatic processes of the squamosals. In all of the above mentioned characters, they are intermediate between the two named forms, but tend towards one or the other as listed. The majority of characters are more as in _ocius_ to which they are here referred. When Goldman (1939:233, 234) listed the named subspecies of _Thomomys talpoides_, he hesitated to include _ocius_ and merely mentioned that _ocius_, _pygmaeus_ and _idahoensis_ might also belong to _talpoides_. Davis (1939:240, 241) found intergradation between _idahoensis_ and _fuscus_ and also between _idahoensis_ and _pygmaeus_, and, therefore, arranged the last two mentioned forms as subspecies of _talpoides_. This present study reveals intergradation between _ocius_ and _uinta_, and also between _ocius_ and _fossor_ (see account of _fossor_). Therefore, _ocius_ is properly to be treated as a subspecies of the series of intergrading forms of which _talpoides_ is the earliest named. All specimens of _ocius_ known from Utah are from the extreme eastern part of the northeastern corner of the state. The type locality of _ocius_ is near Fort Bridger, Wyoming, which is north of Utah. I have seen one specimen from 12 miles west of Linwood, Daggett County, Utah, on Henrys Fork in Wyoming. Additional collecting in northern Utah probably will reveal _ocius_ to inhabit also parts of northern Utah. _Specimens examined._--Total, 4, distributed as follows: _Uintah County_: Vernal, 2 (C. M.); Uncompahgre Indian Reservation, 2 (A. M. N. H.). =Thomomys talpoides moorei= Goldman