ORDER RODENTIA. 147 



brown above. All the under part of the body is white, as 

 well as the interior of the limbs. The sides are gray. The 

 buttocks are marked with a white spot in the form of a 

 crescent. The tail is longer than the body, covered for 

 two-thirds of its length with similar hair, and terminated 

 by a tuft composed of two ranks of hairs, half white and 

 half black. 



The head is oblong, and the muzzle rather protruded, but 

 blunt and thick. The nose is large, flesh-coloured, formed 

 like a heart, with crescented nostrils, divided by a partition. 

 There are eighteen teeth, two incisors in each jaw, four 

 molars in the upper, and three below on each side. The 

 mustachios are formed by long and black hairs. The eyes are 

 large, with a yellow-brown iris. The pupil is nearly round. 

 The ears are longer than the head, half cylindrical, oblong, 

 naked, or nearly so, and transparent. The hinder feet are 

 as long as the body, head included. The tarsus and meta- 

 tarsus are particularly long. In the Skeleton we find only 

 three metatarsian bones, the middle toe of which supports 

 the three principal toes, and is terminated by three articu- 

 lations pulley-formed. The lateral metatarsians are ex- 

 tremely slender, and but half as long as the middle. 



The Alactaga is found in the deserts of Tartary, on 

 the sand-hills which border the Tanais, the Volga, and 

 the Irtisch. This species or variety is not numerous, con- 

 siderably less so than the Gerboa Brachyura. The two, 

 as well as the little Gerboa, inhabit all the region which 

 extends from east to west, from the desert of Crimea, or the 

 neighbouring territories of Taurida Chersonesus, to the 

 countries situated between the Argun and the Onon, and 

 from north to south, from the fifty-fifth degree of north 

 latitude to the tropics. These animals dig very deep bur- 

 rows, but accumulate no provisions there. This we give on 

 the authority of Pallas, but Gmelin says, that they collect 

 herbs arid roots during the summer, form them into different 



