_Thomomys alexandrae_ Goldman, Journ. Washington Acad. Sci., 23:464, October 15, 1933. _Thomomys bottae alexandrae_ Benson, Univ. California Publ. Zooel., 40:449, December 31, 1935. _Type._--Male, adult, skin and skull, No. 250969, U. S. National Museum (Biological Surveys Collection); 5 mi. SE Rainbow Lodge, near Navajo Mountain, Coconino County, Arizona; June 16, 1933; collected by E. A. Goldman; original number 23613 (after Goldman, type not seen). _Range._--In extreme southwestern San Juan County, Utah. Known only from Navajo Mountain, probably limited to the area enclosed on the north by the Colorado and San Juan rivers, on the east and west by Navajo and Piute canyons, respectively. _Diagnosis._--Size small (see measurements). Color: Upper parts Cinnamon Buff, grading over the sides to Pinkish Buff on underparts; nose and top of head grayish black; hind feet and tail white; postauricular patches large and dark. Skull: Small and not heavily ridged; zygomatic arches widely spreading but weak; zygomatic arches nearly parallel; tympanic bullae moderately inflated ventrally; palate not arched; interpterygoid space U-shaped; dentition light. _Comparisons._--Compared to topotypes of _Thomomys bottae absonus_, _alexandrae_ differs as follows: Size smaller in every measurement taken. Color: Upper parts Cinnamon Buff as contrasted with Light Ochraceous Buff. Skull: Smaller in every measurement taken except interorbital breadth and alveolar length of upper molar series which are larger; molariform teeth larger. Among named races of _Thomomys bottae_ occurring in Utah, _alexandrae_ most resembles _T. b. aureus_ to the northeast. It can be distinguished from topotypes of the latter by: Size smaller in every measurement taken. Color: Darker throughout. Skull: Smaller, slenderer and more nearly flat; palate nearly flat as opposed to arched; zygomatic arches weaker and not so widely spreading; interparietal narrower; tympanic bullae smaller; dentition weaker. _Remarks._--Goldman (1933:464) accorded _alexandrae_ full specific status, because he found no intergradation with other races, from which he thought _alexandrae_ had been isolated perhaps for thousands of years by the barriers of the surrounding terrain. Benson (1935:450) noted resemblances between _alexandrae_ and specimens of _latirostris_ from Keams Canyon, Zuni Well, and Winslow in Navajo County, Arizona (= _aureus_), and also between _alexandrae_ and _absonus_ from Houserock Valley, Arizona. He thought that _alexandrae_ is no more differentiated or isolated than each of several other kinds of desert pocket gophers, and, therefore, accorded _alexandrae_ only subspecific status, as I, also, am inclined to do. _Specimens examined._--One (M. V. Z.) from Soldier Spring, Navajo Mountain, 8,600 ft., San Juan County. Fourteen topotypes from Arizona also were examined. MEASUREMENTS OF ADULT MALES OF THOMOMYS (In millimeters)