_Remarks._--The Henry Mountains, in eastern Garfield County, are in the Colorado River drainage. The surrounding country is desertlike and cut by gullies and washes with sheer escarpments and precipitous draws. The type locality of _dissimilis_ is possibly in an isolated area. Only three specimens were available to Goldman when he named _dissimilis_. He commented on the close resemblance to _osgoodi_ which inhabits the country to the north. I have examined only one of the three specimens available to Goldman. Although I can see the characters that he mentioned, I am not fully convinced that _dissimilis_ is separable from _osgoodi_. Two specimens from Escalante, Garfield County, are referred to _absonus_, but they show intergradation with _dissimilis_. _Specimens examined._--One (U. S. N. M.) from E slope Mount Ellen, Henry Mountains, 8,000 ft., Garfield County. =Thomomys bottae aureus= Allen _Thomomys aureus_ Allen, Bull. Amer. Mus. Nat. Hist., 5:49, April 28, 1893. _Thomomys bottae aureus_ Goldman, Proc. Biol. Soc. Washington, 48:156, October 31, 1935; Benson, Univ. California Publ. Zooel., 40:450, December 31, 1935. _Thomomys fulvus aureus_ Goldman, Journ. Washington Acad. Sci., 21:417, October 19, 1931; Journ. Washington Acad. Sci., 23:464, October 15, 1933. _Thomomys perpallidus aureus_ Bailey, N. Amer. Fauna, 39:74, November 15, 1915; Barnes, Bull. Univ. Utah, 12 (No. 15):85, April, 1922; Bull. Univ. Utah, 17 (No. 12):100, June, 1927. _Type._--No. 5243/4123. American Museum of Natural History; Bluff City, San Juan County, Utah; May 12, 1892; collected by Charles P. Rowley (after Allen, type not seen). _Range._--All of San Juan County (except extreme southwestern part) and Grand County east of the Colorado River. _Diagnosis._--Size large (see measurements). Color: Upper parts Cinnamon Buff, lighter on sides; underparts generally white, or if colored at all with only a faint wash of Light Buff; nose and chin blackish gray; top of head blackish due to admixture of black hairs; postauricular patches small and dusky; front feet and hind feet white. Skull: Long, narrow but massive; zygomatic arches not widely spreading, but heavy; jugals thick, union of jugals and zygomatic processes of maxillae thickened; rostrum long but wide; top of rostrum convex in lateral view; ascending processes of premaxillae wide and heavy; nasals thin proximally; braincase long and narrow; tympanic bullae well inflated ventrally; alveolar length of upper molar series long; molars large; pterygoid hamulae heavy; interpterygoid space U-shaped; palate arched; upper incisors long and wide.