11 2 
RODENTS. 
the nose closely pressed to the belly, and the long tail curled round the body, 
which assumes an almost hall-like form. So deep are the slumbers of these 
animals, that they may he 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 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 decuniana), is the 
Jerboa. 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 characterised 
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 
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 
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 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 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 
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 
Range. 
Habits. 
