COUES ON GEOMYS AND THOMOMYS T. TALPOIDES. 257 
Distribution. The most northern specimen I have seen is from the 
Assiniboine River; the species is supposed to range from Hudson's Bay to 
the Rocky Mountains in British America (northern limit unknown). In the 
United States, I have specimens from Minnesota, Dakota, Montana, Idaho, 
Nebraska, Wyoming, Nevada, and Utah. The southern limit is likewise 
unknown, but inferred to be somewhere along the middle of the United 
States. Its range, probably, does not inosculate with that of T. umbrinus; at 
any rate, I have seen nothing intermediate in character from anywhere in the 
Interior. The approach to umbrinus seems to be only made in the Pacific 
province, through bulbivorus. Talpoides exists fairly westward of the main 
chains of the Rocky Mountains; but no Tliomomys of this style is known from 
immediate Pacific slopes. It meets and inosculates with the Northern style 
of bulbivorus ("douglasi") in the Columbia River region. 
Synonymy. The name "talpoides,'' coupled with various generic terms, 
is of frequent appearance in works on natural history; but, so far as I know, 
everything relating to it is pure compilation, the species never having been 
hitherto actually identified. The sole advance upon Richardson's original 
accounts is Audubon's figure of the type-specimen. A difficulty in the way 
of identifying Richardson's animal seems to have been an expression he used 
with regard to the number of digits. But it is morally certain that no such 
difference exists in the genus Thomomys. In some other cases, as in Muridce 
and Sciuridce, strict interpretation of Richardson's remarks in this regard 
would throw his species out of the question ; for he speaks more than once 
of four perfect digits, and a rudimentary one, as in this very case. The 
diagnosis in the Fn. Bor.-Am. is: "grayish-black, with white chin, throat, and 
tail, and only four perfect toes on the hind feet." The expression "cinera- 
scenti-niger'' is no obstacle; for here, as in the genus Geomys, there is a 
plumbago-state of pelage. The "white chin, throat, and tail" are diagnostic, 
in fact, of the animal I here describe, and inapplicable to any other. These 
facts, especially when coupled with the locality assigned (Hudson's Bay), 
leave no doubt in my mind that this is the species indicated by Richardson. 
Furthermore, Audubon's figure from Richardson's type is an unusually faith 
ful representation. I consider this point established. 
The. next names in point of date are ''borealis" and "townsendii," both 
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