OF DENISON UNIVERSITY. 
19 
Being practically subterranean they are little exposed to interrup- 
tion and from their habits little likely to spread rapidly, they multiply 
in favorable localities to an incredible extent and miles of meadow 
land are honey-combed by their burrows. Their natural habitat is 
moist sandy bottom or prairie land where vegetation is succulent and 
the soil yielding. A large river naturally forms an almost insuperable 
barrier to their distribution. The centre for the whole group is in the 
upper Missouri region and various species extend northward into the 
Saskatchewan region and southward into Mexico. The group does 
not extend much east of the Mississippi except in the Gulf States. 
The existing genera are closely related. In New England and the 
Middle States they are entirely absent. There are obvious resem- 
blances in the various members of the Geomyidce to the field mice 
Arvicolince especially in important cranial characters while a more super- 
ficial resemblance, due chiefly to the presence of cheek pouches, allies 
them with the pouched mice or SacconiyidcB. There are many points 
of agreement also with the African mole rats {Georychidce) which they 
more nearly resemble in their habits. 
As just indicated, these low-bodied, rat-like, but densely furred 
animals are chiefly remarkable for the large tur-lined pockets extend- 
ing from the shoulder to the sides of the mouth but opening entirely 
outside the buccal cavity. These pouches have special muscles and 
are used in carrying food which, in all the species, is stored in subter- 
ranean graneries. 
The fur is dense and very soft and mole-like. The under fur is 
plumbeous and very fine. Superficially the color is a subdued but 
rich brown with a purplish or reddish reflection and a glossy bril- 
liancy during life which is lost in the prepared skin. The head and 
middle of the back are darker brown. Beneath, the colors are much 
lighter becoming whitish on the feet, tail and lower lip. There is also 
a light spot on the nose and below the small muffle. The vibrissse 
are thin and pale. The female is lighter. A peculiar phase of color- 
ation not known to correspond to any seasonal or physiological condi- 
tion, occurs in animals which are dark gray, almost black, and uniform 
throughout. In old individuals, there is a considerable admixture of 
white hairs especially upon the head. In summer the feet and tail 
become nearly naked. In form the pocket gopher differs form the 
rat-like rodents in the large relative size of the head and shoulders as 
well as the fore feet. The body tapers rapidly backward and the hind 
