GEOMYIDA:, 809 
level, in the same manner as is witnessed in the case of moles. So 
completely do they live in the ground that one is rarely seen upon it. 
These animals are provided with cheek pouches, some of enormous 
size reaching even to the shoulders, and these are convenient recep- 
tacles for food and afford a means for transporting it from place to 
place. In some localities Gophers are veritable pests, undermining 
the soil with their endless galleries, and flinging the earth excavated 
from these burrows on every side. In size these animals vary con- 
siderably, some being as large as a full grown rat, and others again 
not half that bigness. The pelage is exceedingly soft, even silky. 
The skull is heavy, its muscles large and powerful, and the cutting 
teeth strong and effective, adze-shaped. The family is divided into 
two chief genera, Geomys and Thomomys, distinguished by the 
presence or absence of median grooves on the incisors. 
Fam. 1V. Geomyidz. Pouched Rats. 
C. H. Merriam, Monographic Revision of the Pocket Gophers, N. 
Am. Faun., No. 8, 1895. 
Large, fur-lined cheek pouches present, opening outside the mouth. 
Squamosals expanded; jugal extending to lachrymal; palate sloping 
below level of zygomata, which are strong and flaring; molars rootless; 
lower jaw strong; form arvicoline; fore feet fossorial; eyes and ears 
minute. 
REY TO THE GENERA. 
A. Skull large, flat, rather massive; upper inci- 
sors grooved; jugal extending to lachrymal; 
mandible powerful. 
a. Upper premolar with three enamel plates, the 
posterior absent. PAGE 
a, Uppermaimecisortisuleate..... 2. sce ems Geomys 310 
b.’ Upper incisor unisulcate. 
a.’/’ First and second upper molars with one 
enamel plate each, posterior absent. 
a.’’’ Squamosals not greatly expanded 
laterally; orbitosphenoids articulat- 
ing anteriorly with alisphenoids..... Cratogeomys 
b.’”” Squamosals greatly expanded later- 
ally; orbitosphenoids not articulat- 
ing anteriorly with alisphenoids..... Platygeomys 316 
b.’” First and second upper molars with two 
enamel plates each. 
311 
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