Topotypes of _levis_ differ from near topotypes of _Thomomys talpoides uinta_ as follows: Size larger. Color: Upper parts slightly darker; postauricular patches much darker and larger; ears small and deeply pigmented as opposed to large and lightly pigmented; tail darker all around at base, with white part more extensive and with fewer buff-colored hairs. Skull: More convex dorsally; zygomatic arches more widely spreading and angular; nasals longer; rostrum longer; interparietal wider and more elliptical; posterior ends of nasals rounded as opposed to emarginate; extension of premaxillae posterior to nasals less; pterygoid hamulae more ridged; interpterygoid space more narrowly V-shaped; upper incisors shorter and less procumbent. Topotypes of _levis_ can be distinguished from those of _Thomomys talpoides kaibabensis_ by markedly smaller measurements. For comparisons with _Thomomys talpoides parowanensis_ and _wasatchensis_ see accounts of those forms. _Remarks._--Specimens from the Escalante Mountains and the Aquarius Plateau are not typical. They are of approximately the same color as _levis_, but are larger than _levis_ and have cranial details that indicate intergradation with _kaibabensis_ to the south. They resemble _kaibabensis_ in large size, long nasals and widely spreading zygomatic arches, but are like _levis_ in shape of the interparietal, extension of premaxillae posterior to the nasals, rounded posterior ends of nasals, ridged pterygoid hamulae and relatively short upper incisors. Additional material from these regions may prove these animals to merit separation and naming. _Specimens examined._--Total, 15, distributed as follows: _Sevier County_: Seven Mile Flat, 5 mi. N Fish Lake, Fish Lake Plateau, 10,000 ft., 2 (U. S. N. M.); Fish Lake Experiment Station, 2 (U. S. A. C). _Garfield County_: Posy Lake, Aquarius Plateau, 2 (B. Y. U.); 18 mi. N Escalante, 9,500 ft., 3; Steep Creek, Boulder-Teasdale Road, Boulder Mountain, 4 (B. Y. U.); Summit Birch Creek, Escalante Mountains, 2 (B. Y. U.). MEASUREMENTS OF ADULT MALES OF THOMOMYS (In millimeters)