THE POCKET MICE 1325 



pouches, and their general internal structure, although their upper incisor teeth are 

 proportionately much narrower, and there are certain peculiarities in the conforma- 

 tion of the skull. 



The kangaroo rats are characterized by the molar teeth being root- 

 Common i esS) an( j their best-known representative is the common species (Di- 

 podomys phillipsi} depicted in our illustration, which inhabits the 



desert regions to the eastward of the Rocky mountains, and is charac- 

 terized by the possession of four toes on the hind-feet. The head and body 

 of this animal measure a little over four inches in length; while the tail is very long 

 and tufted at the end, and the general build of the creature light and elegant. The 

 color of the upper parts is mouse brown, becoming tawny on the flanks, while the 

 under parts, the tip of the tail, and a spot above each eye are white or yellowish. 

 In the Rocky mountains the place of this species is taken by Ord's kangaroo rat 

 {/?. ordi) , which is a rather larger and more stoutly -built animal, with a relatively- 

 shorter tail, and having five toes on each hind-foot. 



The habits of the kangaroo rats are very similar to these of the 



jerboas, these Rodents frequenting the most arid districts they can 

 find, and living in burrows made beneath rocks or stones. In such districts there is 

 no water, and but little vegetation save gigantic cactuses; and it appears that the 

 food of the kangaroo rats is formed by the roots, blades, and seeds of the scanty 

 grass that manages to struggle into existence. Probably the only water that these 

 creatures drink is that derived from dew collected on the cactuses. Little or noth- 

 ing seems to be known of their breeding habits. 



THE POCKET MICE 

 Genera Perognathus and Heteromys 



The tiny little Rodents known in the United States as pocket mice are dis- 

 tinguished from the kangaroo rats by the presence of roots to their molar teeth, and 

 also by their inferior size the whole length of the head and body seldom exceed- 

 ing two inches. The genus Perognathus, as represented by the banded pocket mouse 

 (P. fasciatus), of North America, is characterized by the hair being coarse and 

 bristty; whereas, in the genus Heteromys, of which representatives extend as far 

 southward as Trinidad, the fur is mingled with a number of flattened spines. Most 

 of these animals are brownish above and white beneath, with a tawny stripe on the 

 flanks dividing the dark from the light area. 



