ii2 RODENTS. 



the nose closely pressed to the bellj . and the long tail curled round the body, 

 which assumes an almost ball-like form. So deep are the slumbers of these 

 animals, that they rnay be handled for a long time without evincing the slightest 

 signs of life. The young of the various litters are to be met with from May 

 till August. Fossil remains of the jumping mouse occur in the Pleistocene deposits 

 of the United States. 



The Five-Toed Jerboas. 

 Genus Alactaga, etc. 



The jerboas, of which there arc several genera, may be divided into two 

 groups, according to the presence of rive or three toes on the hind-feet, and 

 constitute the second subfamily. The whole subfamily is characterised by the 

 cheek-teeth, of which there may be either three or four pairs, having distinct roots ; 

 by the vertebrae of the neck being more or less completely united together; and 

 by the long metatarsal bones of the hind-limbs being joined together so as to form 

 a cannon-bone, as shown in the figure on p. 110. In all cases only the three 

 middle toes of the hind-feet are of any functional importance; the lateral digits, 

 when present, being small and not reaching the ground. 

 The Kirghiz The kirghiz jerboa, or alagdaga (Alactaga decwmana), is the 



Jerboa. \„.^ known representative of the genus to which it belongs, and is 

 one of the most characteristic mammals of the steppes of Central Asia. The genus 

 Alactaga, in addition to the presence of five toes on the hind-feet, is characterised 

 by its long and tufted tail and huge ears ; there are a pair of premolar teeth in the 

 upper, but none in the lower jaw. and the incisor teeth are not grooved. 



The alagdaga (as the animal is designated by the Mongols) is one of the 



largest members of the group, the length of the head and body being about 



7 inches, and that of the tail considerably more. The general colour of the fur is 



reddish yellow, with a tinge of grey on the upper-parts : while below, as well as 



on the inner sides and lower parts of the hind-legs, it is white; a white patch also 



occurrinji on the outer sides of the thighs. The tail is brown, with a black-and- 



white tip. 



The range of this jerboa includes the whole of the steppe 

 Range. . J . 



districts of Central Asia, and also extends into Persia as far as 



Bushire. and into South-Eastern Europe as far as the Crimea and the region of the 



Don. During the Pleistocene period this jerboa inhabited parts of Germany. 



The alagdaga is a social animal, dwelling in small companies, and 



also selecting such portions of the steppes as possess a clayey soil tor 



the construction of its large burrows. It is strictly nocturnal in its habits, issuing 



from its burrow at the commencement of darkness, but, according to Radde, not 



remaining abroad the whole night. Its speed is said to be considerably greater 



than that of the true jerboa, and the length of its leaps are enormous : indeed, it is 



stated that even when mounted on a swift horse it is impossible to overtake these 



creatures. The burrows constructed by the Kirghiz jerboa are very complicated, 



having several branches radiating from a central chamber; one of these branches, 



it is said, always stops a short distance below the surface of the ground, and is only 



