Of the seven topotypes available to me, six show various degrees of encroachment of the color of the lateral line upon the underparts, giving the ventral surface a buffy appearance, the "distinguishing character" of the subspecies according to Osgood (_op. cit._:20). When additional specimens are available, this character may be found to be one of individual variation, although no specimens from other parts of the range of the species have been found to exhibit it. Of the subspecies _P. f. infraluteus_, each of the eight specimens examined by me possesses buffy subauricular patches. The specimen from 7 mi. N Ramah, Colorado, is slightly darker and less drab than the topotypes and does not possess buffy underparts. The skull of the specimen is broken but on the basis of characters of the pelage it seems to be intermediate between _infraluteus_ and _olivaceogriseus_ and is referred to the former on geographic grounds. _Specimens examined._--Total number, 8, as follows: COLORADO: _Elbert County_: 7 mi. N Ramah, 1 (MZ). _Larimer County_: Loveland, 7 (USBS). =Perognathus fasciatus litus= Cary _Perognathus fasciatus litus_ Cary, Proc. Biol. Soc. Wash., 24:61, March 22, 1911, type from Sun, Sweetwater Valley, Natrona County, Wyoming. _Geographic distribution._--Lower Sweetwater Valley and adjacent parts of Red Desert in Carbon, Fremont, Natrona and Sweetwater counties, Wyoming (see Figure 1). _Remarks._--For comparisons with _Perognathus fasciatus olivaceogriseus_, geographically adjacent to the northeast, see account of that subspecies. From _Perognathus fasciatus callistus_, geographically adjacent to the southwest, _P. f. litus_ differs in: Upper parts paler with no trace of olivaceous; hind foot shorter; skull, when specimens of equal age are compared, averaging smaller in all measurements taken (especially occipitonasal length, mastoidal breadth, length of tympanic bulla and cranial depth), except interparietal breadth which is more. No fully adult specimens of _P. f. litus_ have been available to me for this study. Two of the three specimens mentioned by Cary in the original description (holotype not seen) have been examined and found to possess adult pelage, but cranially they must be classed as young adults. These specimens are paler than those of any other subspecies of _fasciatus_ and do not have the olivaceous dorsal coloration present in other subspecies. _P. f. litus_ is seemingly an endemic race in the lower Sweetwater Valley and adjacent parts of the Red Desert, Wyoming. The type locality, recorded by Cary in the original description as "Sun, Sweetwater Valley, Wyoming," is here placed in Natrona County on the basis of the map (frontispiece) in Cary's (1917) "Life Zone Investigations in Wyoming."