COUES ON GEOMYS AND THOMOMYS. 249 
coast race have larger fore claws than the Southern style of the Pacific-coast 
race or than the Southern Interior race. The difference is sufficient to make 
the whole hand of the former about equal to the foot, while, in the latter, the 
hand is usually shorter than the foot. But this is only true as a rule; there 
are many exceptions. In all three of the forms, the tail, measured from its 
true base, ranges from one-third ta one-half the total length of head and body, 
though only rarely reaching either of these extremes. Nothing can be pred 
icated on this score. 
Color. The .Northern Interior race is a rat-colored animal, hoary-gray 
underneath, with white tail and feet, much white about the mouth, and no 
sooty-blackish there. The Pacific-coast race is a rich dark-brown animal, 
muddy-bellied, with dusky tail and feet, wholly or in part, and sooty about the 
mouth. The Southern Interior race is usually a rich tawriy or fulvous animal, 
with partly dark tail or feet, or both, sooty mouth-parts, and white pouches. 
This race is particularly variable in color ; and, in every respect of color, all 
the races show much variation, and, moreover, intergrade completely. 
The various forms under which the genus Thomomys is exhibited may 
be discriminated, as far as it is possible to do so, by the following characters : 
A. Large. Hind foot an inch or more long. Tail at least 
one-third as long as head and body. Above brown, 
reddish, &c. Below gray, brown, reddish, &c. (not 
white). Ears in a blackish area well developed 1. TALPOIDES. 
a. Six to eight inches long ; fore claws highly devel 
oped (0.45 to 0.55 long), making the hand about 
as long as the foot. Color of the house-rat, 
with white tail and feet, and usually white about 
the mouth and throat ; no contrasts of dark 
color about the mouth. Northern Interior a. talpoides. 
b. Seven to nine inches long ; fore claws less devel 
oped, usually under 0.50, leaving the hand 
shorter than the foot. Reddish-brown, the belly 
muddy-brownish, feet and tail usually not en 
tirely white ; mouth-parts dark, contrasting with 
white of the pouch-lining. Pacific coast b. bulbivorus. 
32 COL 
