J. Knox Jones

“ This impelled me to examine material from the entire range of P. fasciatus. This examination revealed that: (1) Perognathus callistus Osgood, heretofore considered to be a full species, should be reduced to subspecific rank under P. fasciatus; and (2) specimens from eastern Wyoming and adjacent parts of Montana, South Dakota and Nebraska represent an heretofore unrecognized subspecies. Further investigation, however, revealed that Perognathus flavescens olivaceogriseus Swenk, described from northwestern Nebraska (Swenk, 1940:6) , is not flavescens but actually fasciatus. ”

“ 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. ”

“ 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. ”