154 CLASS MAMMALIA. 



The hinder feet are constantly divided into five toes, all 

 nearly of the same thickness. The metatarsus is remarkably 

 long, and formed of as many bones as there are toes. This 

 last is a remarkable distinction between them and the other 

 Gerboas ; the head also is pointed and elongated, and there 

 is a very small projection of the cheek-bones ; while in the 

 others the projection is considerable, on account of the 

 great curvature of the zygomatic arch. The tail is long 

 and proportional to the elongation of the feet. It is always 

 more or less finely annulated, and scaly like that of the 

 Rats ; sometimes covered with hairs, and sometimes almost 

 naked. Its extremity is not tufted, though in certain spe- 

 cies some hairs are longer than others. 



Two of these species, the Mus Tamaricinus and Mus Me- 

 ridianus of Pallas, have been regarded by some naturalists 

 as belonging to the genus Myoxus. This, from a considera- 

 tion of characters, would seem to be an erroneous opinion. 

 The Myoxi, or Dormice, live in trees, and are approximated 

 to the Squirrels by characters sufficiently numerous and im- 

 portant. All the subterraneous animals, such as the Rat, the 

 Hamster, the Marmot, and the Gerboa, have common cha- 

 racters, which group and form them into one natural family. 

 All the known species of Gerbilli dig burrows, and many of 

 them accumulate provisions, which circumstance marks a 

 clear analogy between them and the last-mentioned Rodentia. 



If the Gerbilli are not real Gerboas, (which we are in- 

 clined to believe,) it cannot be denied that the closest affi- 

 nity exists between them. They resemble not only in that 

 external character which is most apparent, namely, the dis- 

 proportion between their anterior and hinder extremities, 

 but also in their mode of living. They walk and run only 

 by leaps, and are possessed of very considerable swiftness 

 of motion. One single species, the Gerbillus of Canada, 

 has been found in a state of hibernation. M. Raffinesque 

 Schmaltz, in the prodromus which he has published on 



