RODENTIA ; RATS, BEAVERS, ETC. 125 



very long. The Jumping Mouse (Fig. 139), is about 

 three inches long, and the tail six inches. It progresses by 

 long and rapid leaps. In winter it hibernates. 



The Hats and Mice or Muridse constitute the most nu- 

 merous family ; the species in all countries, numbering at 

 least three hundred ! 



Some kinds of the Rodents, as the Kangaroo Rats or 

 Saccomyidee have large external cheek pouches, and a 

 slender body; others as the Pouched Gophers or Geomyi- 

 das have large external cheek pouches and a thick body. 

 The species here represented FlG m 



is of the latter family. It is 

 found in the Western States 

 and is eight inches long, be- 

 sides the tail. 



As already indicated the 



IBeavei'S 01* Castoridse are the Pouched Gopher, Geomys lursarius, 



largest of all the living Eo- Richardson. 



dents excepting only the Capybara; and in their habits 

 they are among the most interesting of all the Mammalia. 

 They have a broad flat tail, five toes to each foot, the hind 

 feet webbed, and the second hind toe has a double claw. 

 Their incisor teeth are very sharp and strong, enabling 

 them easily to gnaw down hard-wood trees one or two feet 

 in diameter. They feed mainly upon the bark of the trees 

 which they cut down, and upon roots and aquatic plants. 



Beavers prefer running water, in order that the wood 

 which they cut may be carried to the spot where it is to 

 be used. They keep the water at a given height by dams, 

 which they build of trunks and branches mixed with stones 

 and mud ; and they build houses for winter with the same 

 materials. Each house consists of two stories. The upper 

 story is above water and dry, for the shelter of the animals 



