Remarks.—The specimens used in this study were those recorded by Svihla (1931:261). She reports that they were obtained in the flood-plain banks of the streamsides, and preferred the pine belt. This shows probably an extension of range with reference to life zones, as heretofore the main reported localities of capture have been in sagebrush in the Transition Life-zone.
Insofar as I am aware, Mrs. Svihla's specimens are the only ones of this subspecies ever obtained in Utah. Additional work is necessary in southwestern Wyoming to outline accurately the geographic distribution of this subspecies. In comparison with topotypes, the specimens from Utah are lighter in color and some specimens have slightly larger skulls, suggesting slight intergradation with Thomomys talpoides uinta.
Specimens examined.—Total, 18 (all in Museum of Zoölogy, University of Michigan), distributed as follows: Daggett County: Sheep Creek, 4; 1 mi. W Summit Springs, 4; Beaver Creek, 22 mi. S Manila, 9; Granite Park, 24 mi. S Manila, 1.
Thomomys talpoides ravus new subspecies
Type.—Male, adult, skin and skull, No. 13690, Carnegie Museum; Vernal-Manila Highway, 19 mi. N Vernal, 8,000 ft., Uintah County, Utah; August 22, 1937; collected by J. K. and M. T. Doutt; original number 4718.
Range.—Uinta Mountains in Daggett, northern Uintah and northern Summit counties.
Diagnosis.—Size large (see measurements); ears relatively narrow; hind foot relatively small. Color: Upper parts between Drab and Light Drab, darkest along middorsal line due to mixture of hairs tipped with light brown; sides and flanks Light Drab; entire underparts creamy white; front and hind feet, ventral surface of tail and end of tail white; proximal two-thirds of tail covered dorsally with light brown hairs; nose and cheeks dusky; postauricular patches black. Skull: Large, heavy and ridged; rostrum long and narrow; nasals long, moderately dilated distally and with a distal hump; posterior ends of nasals emarginate; parietal and lambdoidal crests well developed; zygomatic arches moderately heavy and widely spreading, widest posteriorly; zygomatic processes of maxillae moderately heavy and flaring abruptly from base of rostrum; marked middorsal depression in frontals present; interparietal pentagonal; extension of premaxillae posterior to nasals long; posterior tongues of premaxillae long, slender and rounded proximally; braincase high, vaulted and relatively narrow; tympanic bullae well inflated ventrally, and ridged in old animals; pterygoid hamulae long; interpterygoid space narrowly V-shaped; upper incisors long and narrow; molariform teeth medium.
Comparisons.—Compared with topotypes of Thomomys talpoides bridgeri, ravus differs as follows: Size larger; hind foot smaller; ears narrower. Color: Lighter throughout, grayish as opposed to brown. Skull: Smaller, narrower, less angular and less massive; nasals, rostrum, zygomatic processes of maxillae, ascending branches of premaxillae and posterior tongues of premaxillae all narrower; extension of premaxillae posterior to nasals longer; interparietal wider; braincase higher and narrower; tympanic bullae approximately the same size, but more inflated ventrally; interpterygoid space more narrowly V-shaped; upper incisors narrower; molariform teeth weaker.
Compared with topotypes and near topotypes of Thomomys talpoides uinta, ravus differs as follows: Size larger in every measurement taken. Color: Lighter throughout, being grayish as opposed to brown. Skull: Larger in every measurement taken; rostrum and nasals actually as well as relatively longer; extension of premaxillae posterior to nasals longer; upper incisors longer and wider; molariform teeth larger.