336 THE ANIMALS OF THE UNITED STATES 



moderately long tails, and much narrower cheek-pouches than susliks. The 

 common species is the typical prairie- marmot (Cynomys ludovicianus), which is 

 reddish brown with a grey tinge above, and yellowish or brownish white below, with 

 the tip of the tail brownish black. This species is an inhabitant of open plains, 

 and confined to the drier districts east of the Rocky Mountains, ranging from 

 western Texas to the 49th parallel, and from western Kansas to the eastern base of 

 the Rockies. The Mexican prairie-marmot (C. mexicanus) is distinguished from 

 its relative by its larger size, and much longer tail with more black at the tip. 

 Other species found in the United States are Gunnison's prairie-marmot (C. 

 gunnisoni) of Arizona and New Mexico, which is smaller than the type species. 

 Lewis's prairie-marmot (C lewisi) of Wyoming and the adjacent territories, and 

 the Arizona prairie-marmot (C. arizonensis) of southern Arizona. These rodents, 

 which associate in large colonies, live in separate holes, each having a small heap of 

 earth in front of the entrance. There are generally three or four entrances all 

 belonging to the same burrow, each burrow having perhaps ten or twelve in- 

 habitants. The common prairie-marmot is distinguished from some of the other 

 species by forming funnel-shaped entrances to its domicile from the earth thrown 

 out in burrowing, which is heaped up with the fore-feet, and pressed down in 

 damp weather with the nose. 



North America is the sole home of a family of remarkable 

 Sewellels. . . 



rodents, the sewellels, whose members are in habits half-beavers and 



half-squirrels. They owe their scientific name (Haplodontidce) to the structure 

 of their cheek-teeth, which are without roots, and the first pair of which in the 

 upper jaws are extremely small. Speaking generally, sewellels are stoutly built 

 rodents, with a head somewhat recalling that of a pug-dog, the body cylindrical, 

 and the tail a mere stump. The Californian representative of the genus, the so- 

 called mountain-beaver (Haplodon rufus), is a fairly large rodent of about 16 

 inches in length, typically inhabiting the cascades of the Columbia River, but 

 represented by varieties in California and Washington. This rodent resembles 

 a squirrel in its climbing propensities, but in other respects is more like a 

 beaver, since it inhabits wet ground with plenty of running water, where it forms 

 small colonies and makes its burrows on sloping ground in such a manner that 

 water can pass through them. 



Although the mouse tribe is abundantly represented in the 

 Mouse Tribe. ~ , 



continent of America from one extremity to the other, there are no 



members of the true rats and mice indigenous to the New World. Their place is 

 taken by voles generically identical with the European forms and by a vast number 

 of forms more or less nearly allied to the hamsters of Europe and Asia. Many of 

 these cricetines are distinguished by white feet, and are therefore called white- 

 footed mice, but in shape and in the length of tail the group varies greatly. Some, 

 for instance, have long tails and resemble common mice ; others look like dormice ; 

 others again have short hamster-like tails and bodies like voles, and one species is 

 distinguished by spines growing among its hair. It is now the fashion to refer 

 these cricetines to quite a number of genera, of which the following are represented 

 in the United States : namely, Onychomys, Peromyscus, Sigmodon, Oryzomys, and 

 Rhithrodontornys. One of the most familiar species is the common deer-mouse 



