COUES ON GEOMYS AND THOMOMYS T. TALPOIDES. 255 
sharp spicule, clubbed at base, tapering and slightly curved, nearly three- 
quarters of an inch long. In a female, I have distinctly made out twelve 
mammae, of which two pairs are inside the thigh, two pairs on the chest, and 
two pairs axillary. 
Few, however, if any, of the foregoing points are diagnostic of the spe 
cies ; nor will the ensemble serve-to distinguish it infallibly from its congeners, 
excepting T. dusius. As to form, the single character I notice is the greater 
average development of the fore claws, bringing the length of the hands up 
to about that of the feet. Some points of color about to be noticed are the 
most reliable distinctions. The animal is as nearly as possible like the house- 
rat (Mus decumanus}. The whole upper parts are of a uniform grayish-brown, 
generally quite pure, though occasionally warming into a more reddish-brown. 
But, in the most reddish specimens, the tint is uniform, without the peculiar 
mottling or lining of a dark-brown with a reddish-brown which constitutes 
the richer color of the Pacific-coast bulbivorus. The only departure from the 
uniformity of the upper parts is a small blackish patch, usually very evident, 
in which the ears are set. On the sides of the body, the color gives way 
gradually to the lighter tint of the under parts : here we find the plumbeous 
of the roots of the hairs as a background to a hoary-grayish, resulting from 
the tips of the hairs. This hoary is usually quite pure, but it sometimes 
takes on an appreciably muddy-brown tinge, still never equaling, as far as 
known, the richer fulvous-brown which tones the under parts in the coast 
form. The tail and feet are white in every specimen I have seen ; and, besides 
this, there are usually patches about the mouth, cheeks, throat, and breast, 
where the fur is pure white to the roots. But these white markings are 
wholly indeterminate in extent, as well as inconstant in appearing at all; in 
many cases, the parts are concolor with the rest of the under surface. Per 
haps the strongest color-mark of the species is the absence from any part of 
the head of sooty-blackish or even dusky areas, there being no noticeable con 
tracts of color between the mouth-parts and pouches ; whereas, in T. bulbi 
vorus, and, still more so, in umbrinus, these parts are dusky, or even coal-black, 
contrasting sharply with the pure-white linings of the pouches. The whiskers 
are mostly colorless; the claws are colorless, though usually stained with 
extravasated blood. 
Northern Dakotan and Minnesota!! specimens may be taken to represent 
