RODENTS. 



distinctive features in the skull, more especially in the large size of the hinder 



part of the auditory bulla, into which it would be out of place to enter here. 



The jerboas and their allies are mainly Asiatic 

 and African forms, although there is one outlying 

 species in North America, and a few range into 

 Southern Europe. Most of the jumping kinds are 

 inhabitants of open and dry districts, such as grassy 

 steppes or sandy deserts; and approximate in colora- 

 tion very closely to that of the ground on which 

 thej' dwell. They form burrows in clayey or sandy 

 soil, which are generally situated in the open plains, 

 but sometimes among thicker or thinner bush-jungle. 

 In habits they are mostly nocturnal, lying concealed 

 in their burrows by day, and issuing forth to feed 

 at night. Their nutriment consists of roots, berries, 

 seeds, fruits, leaves, grass, and other herbage : but a 

 few will also eat insects, small birds, and carrion. 

 In feeding they sit in a half-erect posture upon their 

 hind-quarters and tail, and convey the food to their 

 mouth with the aid of their paws. Their move- 

 ments are peculiar: the body being supported on 

 the hind-limbs alone, perhaps aided, however, at times 

 by the tail. In walking, the legs are moved alternately 

 in the ordinary manner ; in which respect these animals 

 differ from kangaroos, which always hop. Progression 

 at a more rapid rate is, however, always effected by a 

 series of leaps from the hind-legs: the length of such 

 lea] is being generally very great in proportion to the 

 size of the animal. Like all desert-haunting animals, 

 the jerboas are extremely quick of hearing and long- 

 sighted. Although generally silent, many of these 

 animals have a kind of whining cry, which has been 

 compared to that of a kitten. In the colder districts 



of their habitat, the species hibernate more or less completely; but they never 



lay up a store of provisions for winter use. 



The family may be divided into four main groups or subfamilies. 



SKELETON of jehboa. 



The Jumping Mouse. 



Genus Zap vs. 



The so-called jumping mouse of North America (Zapus hiulsonianus) is the 

 typical representative of the first group of the family. It is characterised by the 

 presence of four pairs of rooted cheek-teeth in each jaw, by the vertebrae of 

 the neck being entirely separate from each other, and by the long hind-limbs 

 being furnished with five complete toes, of which the metatarsal bones are 



