222 EXPLORATION OF THE CANONS OF THE COLORADO. 
of the fur plumbeous throughout ; or blackish-gray ; feet and tail, for the 
most part, white or colorless. Average dimensions of adult, 7 to 8 inches ; 
tail, 2 or 3 inches ; fore foot, about 1| inches ; hind foot, about \\ inches ; 
longest fore claw, about 0.75 inch. 
HABITAT. Valley of the Mississippi and its tributaries in a broad sense, 
and somewhat beyond to the northward. "Canada." " Oregon " (111). 
DESCRIPTION. I shall draw up my account of this species from the large 
amount of material, both dry and alcoholic, before me. The specimens are 
from the whole immediate valley of the Mississippi, from the State of that 
name to Minnesota ; also, from Texas ; from the Platte, Washita, and Nio- 
brara Rivers, &c.; but not from west of the Rocky Mountains, where the 
genus has yet to be satisfactorily determined to occur. Descriptions of form 
and proportions are taken from alcoholic specimens in the flesh ; of color, 
from dried specimens. The present being taken as the standard of compari 
son for other species, succeeding descriptions of the rest may consequently 
be abridged to present in stronger light their own peculiar characters. The 
present account, besides being descriptive of the particular species, is ren 
dered supplementary to the characters of the genus. 
The "pocket-gopher" is about the size of a house-rat (Mus decumanus\ 
but less in linear dimensions and much more stoutly built, with a heavy, 
lumpy body, on which the skin slips loosely ; no appreciable neck ; a rapidly 
narrowed blunt head ; small eyes ; no obvious external ears ; short limbs ; 
strong fore feet, somewhat like those of a mole, with enormous claws ; and a 
short, thick, stumpy tail, issuing from a conical prolongation of the rump. 
The side of the body, before the shoulder, is occupied by an enormous sac, 
opening by a wide slit along the side of the jaws, but not directly communi 
cating with the mouth. These sacs, fully distended, represent the greatest 
crosswise dimension of the animal. To sum the generalities, the gopher is a 
mole-like rat, plus these great bags. The general habits bear out the simile : 
of all rodents, the gopher is probably the most completely fossorial and sub 
terranean; and its underground operations are conducted with the aid of 
theSe sacs. 
The head is short, wide, deep, and blunt ; not separated from the body 
by any appreciable constriction of the neck. The frontal region is broad and 
