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."

_Specimens examined._--Total number, 9, as follows: WYOMING:
_Carbon County_: 8 mi. SE Lost Soldier, 6700 ft., 1 (USBS).
_Fremont County_: Granite Mts., 1 (MZ). _Natrona County_: 5 mi. W
Independence Rock, 6000 ft., 4 (KU); Sun, 1 (USBS); 16 mi. S, 11
mi. W Waltman, 6950 ft., 1 (KU). _Sweetwater County_: 27 mi. N
Table Rock, 1 (MZ).

=Perognathus fasciatus callistus= Osgood

_Perognathus callistus_ Osgood, N. Amer. Fauna, 18:28, September
20, 1900, type from Kinney Ranch, near Bitter Creek, Sweetwater
County, Wyoming.

_Geographic distribution._--East of the Green River in central and
southern parts of Sweetwater County, Wyoming, and adjacent parts of
Moffat County, Colorado (see Figure 1).

_Remarks._--For comparisons with _Perognathus fasciatus litus_,
geographically adjacent to the north, see account of that subspecies.

When Osgood (_loc. cit._) described _P. f. callistus_ as a full species,
he characterized it as having " ...