1284 THE RODENTS 







locality and the temperature of the season. In mild winters the hibernation is often 

 interrupted for longer or shorter periods. The underground nest is carefully made 

 of grass, in which the little animal lies tightly curled up, with the nose closely 

 pressed to the belly, and the long tail curled round the body, which assumes an al- 

 most ball-like form. So deep are the slumbers of these animals, that they may 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 are several genera, may be divided into two groups, 

 according to the presence of five or three toes on the hind-feet, and constitute 

 the second subfamily. The whole subfamily is characterized 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; and by the long 

 metatarsal bones of the hind-limbs being joined so as to form a canon bone, 

 as shown in the figure on p. 1282. 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 jerboa, or alagdaga (Alactaga decumana], is the best- 

 . . 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 charac- 

 terized by its long and tufted tail and large 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 seven inches, 

 and that of the tail considerably more. The general color of the fur is reddish 

 yellow, with, a tinge of gray 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 occurring 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 districts of 

 Central Asia, and also extends into Persia as far as Bushire, and into 

 Southeastern 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 for 

 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 re- 

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

 that of the true jerboa, and the length of its leaps is enormous; indeed, it is stated 



