456 MAMMALIA. 



more striking. The tail is long and covered Trith short hair, 

 and terminated by a tuft ; the coat is soft and thick. 



The Jerboa inhabits the vast solitudes of Africa, and the steppes 

 of Tartary and Russia. They dig out burrows, in which they 

 pass the day, sleeping on a bed of grass and moss. But in the 

 evening they seek their food, which consists of roots and seeds. 

 They make use of their fore paws to convey what they eat to their 

 mouths. 



Under ordinary circumstances, when nothing occurs to hurry or 

 excite them, the Jerboas walk on all fours ; but if, from the 

 scarcity of sustenance, or the necessity of escaping from danger, 

 they are compelled to go a considerable distance in a short 

 space of time, they use their hind legs only, moving forward in 

 leaps, like the Jerboa-Rats ; but the span of their bounds is of 

 much greater extent, reaching sometimes to three yards. The 

 'waj in which these springs are made is very curious. The 

 animal first crouches down on its tarsi, at the same time stretch- 

 ing out and stiffening its tail, so as to make another bearing- 

 point on the ground ; then, suddenly, it bounds forward, as if 

 forced by a spring. The same manoeuvre is repeated after an 

 imperceptible interval of time. It is said that the Jerboa can 

 compete in speed with a fast horse. The ancients, looking at 

 this peculiar mode of progression, were led to think that the 

 fore legs of these Rodents were absolutely unfitted for walking, 

 and for this reason gave them the name of Dipus, which signifies 

 two-footed. 



Jerboas are difficult to tame ; they can, however, be kept in 

 cages ; and the menagerie of the Jardia des Plantes at Paris is in 

 possession of several specimens. It is necessary to place them in 

 cages made of iron wire, for the hardest wood cannot resist 

 their jaws. Their size varies from that of the Mouse to that of 

 the Brown Rat. 



Among the numerous species which are known, we will mention 

 one which is common in Algeria, especially in the province of 

 Oran, the Alactaga, called also by the significant name of Sagitta, 

 or Arrow, which is also a native of Southern Russia and some 

 parts of Asia. 



The Pedefes Genus. — The Great Jerboa, or Jumping-Hare, or 

 Spring-Hare of the Colonists, and Helamys, are the representa- 



