680 MONOGRAPAS OF NORTH AMERICAN RODENTIA. 
or grayish-white, rarely with faint annulations of black. In summer speci- 
mens, there is generally a more or less distinct black lateral line ;.in many, 
it is, however, nearly obsolete, and is sometimes wholly absent, as it appears 
to be generally in winter specimens. The tail is black, edged with gray; the 
terminal third, however, often wholly black. The tail-hairs are at the base 
generally gray, but sometimes more or less fulvous, and even rufous. 
In this variety, the middle of the back is not generally redder than the 
rest of the dorsal surface; the reddish dorsal band, so characteristic of the 
other varieties, being absent. The general color above is hence nearly uniform 
gray, more or less strongly tinged with yellowish- or reddish-brown. The 
tail generally has also no fulvous or rufous at the base of the hairs, which are 
gray at base and tipped with whitish. These are the two principal features 
of distinction between the present variety and vars. richardsont and douglassi. 
Specimens, however, from various localities, have more or less red or fulvous 
at the base of the tail-hairs, and, in some specimens, the tail is washed with 
pale yellowish instead of white. In the extreme phase of this species, the 
tail is centrally above pure light gray, sometimes tinged slightly with yel- 
lowish or. rufous. No. 11679, from Fort Garland, Colo, has the tail 
centrally reddish-yellow to the end of the vertebra, and edged with pale 
yellowish-white. The general color varies from pale fulvous, varied minutely 
with black, to strong yellowish-rufous. The sides are usually paler than the 
back, but there is never a well defined dorsal band. ‘The feet and outer side 
of the limbs are frequently golden. 
Var. fremonti ranges from the eastern base of the middle portion of the 
Rocky Mountains to the Pacific (some of the specimens from Fort Crook, 
Cal., being undistinguishable from Colorado ones) and from New Mexico 
to Southern Montana and Idaho. Specimens from Bear Creek, Oregon, 
and from the Uintah Mountains are typically of this variety; Fort Bridger 
specimens are nearly so. Jarther northward, it passes into var. richardsoni, 
and in California merges imperceptibly into var. dowglaszi. Several of the 
California specimens (Nos 3848 and 3846, from Fort Crook) have the under 
parts pure white, the tail centrally gray and washed with white, and the 
upper surface uniformly colored; hence closely resembling var. fremont. 
Others (Nos. 3316 and 4664), from the same locality, are strongly fulvous 
beneath, like some (No. 1160, for example) of the specimens from the Upper 
Des Chutes Valley, and even more strongly so than Nos. 1956 and 1420, 
