150 RODENTS. 



the yellowish skin is almost naked, save for a few sparsely scattered hairs. One of 

 the two species has three pairs of molar teeth in each jaw, while in the other there 

 are but two. 



These sand-rats are entirely subterranean in their habits. Mr. Lort Phillips 

 states they throw up "groups of miniature craters, which exactly represent 

 volcanoes in active eruption. When the little beasts were at work I used frequently 

 to watch them, and found that the loose earth from their excavations was brought 

 to the bottom of the crater, and sent with great force into the air in a succession of 

 rapid jerks, but they themselves never venture forth from the shelter of their 

 burrows." 



THE AMERICAN POUCHED RATS. 

 Family GEOMYIDJE. 



The possession of large cheek-pouches lined with hair, which open externally 

 to the mouth at the lower edges of the cheeks, forms the distinctive peculiarity of 

 a family of rat-like Rodents confined to the New World. The forms included in 

 the family vary considerably in external appearance and habits; its larger and 

 burrowing representatives being known as pocket -gophers, while the smaller 

 terrestrial types are respectively termed kangaroo -rats and pocket -mice. In 

 addition to three pairs of molar teeth with transverse plates of enamel on their 

 crowns, and which may or may not be rooted, all these Rodents have a single pair 

 of premolar teeth in each jaw. Their skulls are characterised by the great twisting 

 of each branch of the lower jaw, and likewise by the forward extension of the 

 cheek-bone. 



POCKET-GOPHERS. 



Genera Geomys and Thomomys. 



The pocket-gophers include large rat-like species, with burrowing habits, and 

 are characterised by their small eyes, rudimental external ears, and the equality 

 in length of their comparatively short limbs. The whole of them are confined to 

 North and Central America. 



Common Pocket- The common pocket-gopher (Geomys bursarius) is selected for 

 Gopher. illustration as the best known representative of the group, and as 

 being the type of the genus Geomys, characterised by the presence of a deep groove 

 on each of the broad upper incisor teeth. This species attains a length of from 7 

 to 8 inches from the muzzle to the root of the tail ; while the hairy tail itself 

 varies from 2 to 3 inches. The fur is of a soft and mole-like texture ; and of a 

 beautiful reddish brown colour above, becoming greyish beneath, while on the feet, 

 and generally also on the tail, it is white. 



This pocket-gopher is an inhabitant of the extensive plains of the valley of 

 the Mississippi and its tributaries, extending somewhat beyond these limits to the 

 northwards. Here it lives a mole-like life, constructing subterranean tunnels and 

 throwing up at intervals conical heaps of earth, after the fashion of the " little 

 gentleman in black velvet." The tunnels generally run at a distance of about a 



