260 EXPLOITATION OF THE CANONS OF THE COLORADO. 
strong wash of tawny or muddy-brown, quite unlike the hoary-gray of the 
same parts of talpoides. The under surface is not known to be varied with 
patches of white, nor is there any white about the mouth, excepting the 
immediate border of the lips. On the contrary, the mouth-parts are sooty 
or dusky, contrasting with the white which lines the cheek-pouches. This 
is very much as in umbrinus, and quite different from talpoides. The hands 
and feet are sometimes white, as in talpoides, but oftener merely whitish, and 
not seldom dusky. I have not seen the tail pure white ; it is generally dark- 
colored for the most part, often wholly so. The fore claws average about 
0.40 rather less than more. 
Such is the typical manifestation of this form, which I have only seen 
from California. We have next to trace the change by insensible degrees 
into both talpoides and umbrinus. Proceeding up the Pacific coast, we find 
an animal still like bulbivorus in the general tone of coloration (warm-brown 
above and muddy-bellied), but in which the mouth-parts have nearly or 
entirely lost their sootiness. Here, also, the fore claws enlarge somewhat, 
and from this state it is but a step to the grayer true talpoides, which joins 
with douglasi in the interior of Oregon and Washington. In the interior 
of California, the opposite modification begins, tending toward umbrinus, 
which becomes fully established in Arizona and New Mexico. Here the 
dark mouth-parts are preserved and even intensified, but the color grows 
richer till a decidedly tawny or fulvous cast is the result. Various specimens 
from Fort Crook and Fort Tejon, and from Provo, Utah, are of this ambig 
uous sort, and exhibit among themselves such variations that their labeling 
becomes a matter of indifference. Some of the browner ones are not 
separable at all from bulbivorus, while the ruddiness of others matches that 
of true fulvus. The gradation of the two forms in this region is demonstrable 
complete. Some other specimens from Fort Crook are absolutely identical 
with Steilacoom ones in respect of color; the only difference I can note being 
the somewhat weaker claws. To the southward, on the coast, the same 
gradation occurs, becoming established about San Diego, In Lower Cali 
fornia, pure umbrinus prevails. 
A San Franciscan specimen lately received at the Smithsonian is a 
perfect albino snow-white all over. 
