_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. _Remarks._--Twenty-one animals obtained from Lynndyl, Millard County, are all intergrades between _lenis_ and _aureiventris_. They are like _aureiventris_ in the shape of the zygomatic arches, and in the bowing of the parietal crests. Slight intergradation with _centralis_ is indicated by color and the shape of the nasals. The transverse arching of the posterior part of the rostrum is indicative of some relationship with _contractus_. In six other characters studied they most closely approach _lenis_ to which they are here referred.