_Type._--Male, adult, skin and skull, No. 158530, U. S. National Museum (Biological Surveys Collection); Hanksville, Wayne County, Utah; October 20, 1908; collected by W. H. Osgood; original number 3701 (after Goldman, type not seen). _Range._--Eastern Utah in the valleys of the drainage of the San Rafael, Dirty Devil and Price rivers. _Diagnosis._--Size medium (see measurements). Color: Upper parts near (_e_) Pale Ochraceous Buff, definitely yellow in appearance; sides Pale Ochraceous Buff; entire underparts white, with a wash of Light Buff in the pectoral and inguinal regions; top of head, nose, cheeks, and chin dusky; postauricular patches grayish black; front feet, hind feet and distal part of tail white. Skull: Fairly robust but narrow; zygomatic arches concave medially in mid-jugal region; skull moderately convex dorsally, due to swelling in region of base of rostrum; lambdoidal suture situated well ahead of posterior margin of skull, with supraoccipital forming a side shelf at posterior part of skull; interpterygoid space narrowly V-shaped; tympanic bullae well inflated ventrally; basioccipital short; nasals rounded posteriorly; molariform teeth large. _Comparisons._--Topotypes of _osgoodi_ differ from those of _Thomomys bottae absonus_ as follows: Size generally smaller. Color: Lighter throughout, more yellowish in appearance as opposed to buffy. Skull: Smaller in all measurements, except length of nasals, mastoid breadth, and alveolar length of upper molar series which are larger; rostrum shorter but relatively wider; zygomatic arches more robust and concave medially; palate wider; supraoccipital more bulging posteriorly; tympanic bullae more inflated ventrally; molariform teeth larger. For comparisons with _Thomomys bottae aureus_ and _T. b. dissimilis_ see accounts of those forms. _Remarks._--The animals here referred to _osgoodi_ are remarkably uniform in color, but vary widely in cranial details. Specimens from Carbon County are not typical and when more material becomes available it may prove that these animals from the northern part of the range of _osgoodi_ will merit separation and naming. The specimens from Emery County are not typical but resemble _osgoodi_ more than do the animals from Carbon County.