Topotypes of _wasatchensis_ can be readily distinguished from those of _Thomomys talpoides levis_ and _parowanensis_ by larger size; more massive, ridged, angular skulls; larger tympanic bullae; large, ovoid foramen magnum; and relatively smaller interparietal.
_Remarks._--Specimens from Mount Timpanogos and environs are intergrades between _moorei_ and _wasatchensis_. They resemble _moorei_ in the shape and size of the tympanic bullae, and are intermediate in the size and shape of the foramen magnum. In the majority of characters they resemble _wasatchensis_ to which they are here referred. The animals from east of Salt Lake City in Salt Lake County are intergrades between _oquirrhensis_ and _wasatchensis_ and show some characters of _uinta_, but are referable to _wasatchensis_. Animals from Morgan County and western Summit County are intergrades between _wasatchensis_ and _uinta_. They resemble _uinta_ in size, shape of nasals and size of tympanic bullae. The remainder of the cranial details place them with _wasatchensis_. Morphologically the animals from Wellsville, Cache County, were the closest to the topotypes of any obtained and are nearly indistinguishable from them. Like the topotypes of _wasatchensis_ this population inhabits a high valley. The remaining specimens from Cache County resemble those from Morgan and Summit counties.
_Specimens examined._--Total, 119, distributed as follows: _Cache County_: Logan Canyon, Beaver Basin, Utah-Idaho Line, 2 (U. S. A. C); Logan Canyon, Tony Grove Camp, 6 (U. S. A. C); Logan Canyon, Green Camp, 3 (U. S. A. C); Logan Canyon, 3 (U. S. A. C); Logan Mountains, 20 mi. E Logan, 3 (U. S. A. C); Logan Peak area, 13 (U. S. A. C); near Providence Peak, Logan Mountains, 1 (U. S. A. C.); Wellsville, 10 (U. S. A. C); Hardware Ranch, Blacksmith Fork, 1 (U. S. A. C); Avon, 1 (U. S. A. C); 1 mi. E Avon, 1 (U. S. A. C); 7-8 mi. E Avon, 1 (U. S. A. C). _Weber County_: South Fork, Ogden River, 18 mi. E Ogden, 4 (M. V. Z.). _Morgan County_: East Canyon, 18 mi. NW Park City, 6,000 ft., 1. _Davis County_: 8 mi. NE Salt Lake City, 1. _Salt Lake County_: Mouth of Dry Canyon, 1 mi. NE Salt Lake City, 1; 4 mi. above mouth City Creek Canyon, 5,000 ft., 1; mouth of Emigration Canyon, 1; mouth of Millcreek Canyon, 1; Lambs Canyon, 13 mi. SE Salt Lake City, 2 (C. M.); mouth of Big Cottonwood Canyon, 1. _Summit County_: Park City, 1 (U. S. N. M.). _Wasatch County_: Midway, 5,500 ft., 29. _Utah County_: Mt. Timpanogos, 1 mi. N Aspen Grove, 7,500 ft., 20; Aspen Grove, Mt. Timpanogos, 5 (1, U. S. A. C.; 4, B. Y. U.); Head of Grove Creek, Mt. Timpanogos, 4 (B. Y. U.).