_Specimens examined._--Total, 39, distributed as follows: _Millard County_: Oak City, 5,000 ft., 15; Scipio, 5,315 ft., 15. _Beaver County_: Beaver, 6,000 ft., 9 (M. V. Z.).
_Thomomys townsendii lenis_ Goldman, Proc. Biol. Soc. Washington, 55:75, June 25, 1942.
_Thomomys perpallidus aureus_ Moore, Journ. Mamm., 10:259; November 11, 1931.
_Type._--Male, adult, skin and skull, No. 264805, U. S. National Museum (Biological Surveys Collection); Richfield, 5,308 ft., Sevier County, Utah; March 11, 1928; collected by A. W. Moore; X-catalogue number 28835 (after Goldman, type not seen).
_Range._--Sevier River Valley from Piute County north to southwestern Juab and northeastern Millard counties, Utah.
_Diagnosis._--Size large (see measurements). Color: Upper parts Cinnamon Buff mixed with black in middorsal region; sides, flanks, forearms, thighs and underparts Pinkish Buff; inguinal region, front feet, hind feet, underpart of tail and end of tail white; postauricular patches small and dusky; chin, cheeks, nose and top of head dusky. Skull: Largest of Utah gophers, massive and angular; nasals long and denticulate distally; rostrum long and relatively narrow; zygomatic arches widely spreading and heavy throughout; jugals nearly vertical; zygomatic processes of maxillae heavy and flaring out abruptly from base of rostrum; union of zygomatic process of maxilla and jugal greatly thickened; extension of premaxillae posterior to nasals long; posterior tongues of premaxillae relatively narrow; lacrimal processes small; pterygoid hamulae long; interpterygoid space moderately V-shaped, tending to be somewhat lyre-shaped in some specimens; tympanic bullae somewhat flattened, only moderately inflated ventrally; upper incisors long and narrow; molariform teeth actually large, but relatively small.
_Comparisons._--Topotypes of _lenis_ can be distinguished from those of _Thomomys bottae tivius_, _convexus_, _contractus_, _albicaudatus_, _levidensis_, _centralis_ and _aureiventris_ by the following markedly greater average measurements of males: Total length, 250 mm.; length of nasals, 15.5; zygomatic breadth, 28.3; mastoid breadth, 22.5; and length of rostrum, 18.3. Other distinguishing characters are: Zygomatic arches more widely spreading; length of zygomatic processes of maxillae greater; and relatively longer, narrower rostrum.