From the time of the original description of _aureus_ in 1893 until 1930, all light colored gophers from Utah were referred to that form. Barnes (1927:100) gives the range of _aureus_ as extending completely across southern Utah and on the west and east sides as far north as central Utah. Since 1930, forms named by E. R. Hall, W. H. Burt, E. A. Goldman and the writer have restricted the range of _aureus_ in Utah to that part of the state east of the Colorado River. _Specimens examined._--Total, 22, as follows: _San Juan County_: Bluff, 3,300 ft., 22 (15, M. V. Z.). =Thomomys bottae birdseyei= Goldman _Thomomys bottae birdseyei_ Goldman. Proc. Biol. Soc. Washington, 50:134, September 10, 1937. _Thomomys perpallidus aureus_ Bailey, N. Amer. Fauna, 39:75, November 15, 1915; Barnes, Bull. Univ. Utah, 12 (No. 15):85, April, 1922; Bull. Univ. Utah, 17 (No. 12):100, June, 1927. _Type._--Male, adult skin and skull, No. 161654. U. S. National Museum (Biological Surveys Collection); Pine Valley Mountains, 5 mi. E Pine Valley, 8,300 ft., Washington County, Utah; April 10, 1909; collected by Clarence Birdseye; original number 861 (after Goldman, type not seen). _Range._--High mountains and plateaus of southwestern Utah. _Diagnosis._--Size medium (see measurements). Color: Upper parts between Cinnamon and Sayal Brown, finely mixed with black in median dorsal region, grading over sides and flanks to Cinnamon on underparts; front feet, hind feet, and distal part of tail white; postauricular patches, chin, cheeks and top of head grayish black. Skull: Depressed along median line of frontals and posterior ends of nasals; region of nasofrontal suture concave ventrally; zygomatic arches heavy and widely spreading, widest posteriorly; posterior ends of nasals straight, tending to be somewhat rounded in some specimens; extension of premaxillae posterior to nasals moderate; tympanic bullae moderately inflated ventrally; basioccipital wide; interpterygoid space widely V-shaped. _Comparisons._--Topotypes of _birdseyei_ differ from near topotypes of _Thomomys bottae virgineus_, from Beaverdam Wash as follows: Size larger; tail and hind foot longer. Color: Darker throughout, between Cinnamon and Sayal Brown as opposed to Cinnamon Buff. Skull: Larger in every measurement taken except extension of premaxillae posterior to nasals, and length and width of rostrum which are less; skull more depressed in nasofrontal region; zygomatic arches more widely spreading; zygomatic processes of squamosals shorter; pterygoid hamulae longer; tympanic bullae smaller and less inflated ventrally.