E. Raymond Hall

“ In the initial study, one of us, Montague, separated the material from the Medicine Bow Range in Wyoming as a subspecies different from that at Laramie and the adjoining mountains to the eastward because of the darker color of the western animals and the smaller size of males. Acquisition of more material from still farther west (Sierra Madre) in Wyoming and the examination of material in the United States Biological Surveys Collection from Colorado discloses that there is a cline of increasing intensity of color from the geographic range of T. t. ”

“ In the academic year of 1947-48 Montague studied the geographic variation in Thomomys talpoides of Wyoming. His study was based upon materials then in the University of Kansas Museum of Natural History. Publication of the results was purposely delayed until previously reported specimens from certain adjacent areas, especially in Colorado, could be examined. In the autumn of 1950 one of us, Hall, was able to examine the specimens from Colorado; also, the specimens from Wyoming accumulated in the past two seasons of field work in Wyoming were examined by Hall. ”

“ From Thomomys talpoides fossor (specimens from Rico, Silverton, Hermit and Pagosa Springs, all in Colorado) , the subspecies to the southward, T. t. rostralis differs in: Longer body; lighter color of upper parts; nasals truncate rather than rounded posteriorly; temporal ridges more nearly parallel (less divergent posteriorly) ; rostrum longer (averaging longer and broader) ; skull wider across zygomatic arches in 11 of 12 specimens of rostralis.
Remarks.—Geographic variation is evident in the material examined. ”