148 MAMMALIA. 



and roots. The limbs are short ; there is scarcely any tail ; and 

 the eyes are excessively small. From Siberia ; where it always 

 lives under ground like the Mole and Rat-Mole. It feeds prin- 

 cipally on the bulbs of different Liliaceae. The third species, like 

 the other animals comprised in the great genus of Rats, has 

 merely the rudiment of a thumb on the fore foot. 



G. Iiudsonius ; Mus hudsonius, Gm., Schreb. CXCVI. (The 

 Lemming of Hudson's Bay.) A light pearly-ash colour ; with- 

 out tail or external ears ; the two middle toes of the fore foot of 

 the male seem to have double claws, which is owing to the skin 

 at the end of the toe being callous and projecting from under 

 the nail, a disposition of the part hitherto vmknown, except in 

 this animal. It is the size of a Rat, and lives under ground- in 

 North America. 



Otomys, Fred. Cuv. 



The Otomys are nearly allied to the Field Rats, and have also 

 three grinders, but they are composed of slightly arcuated laminse 

 arranged in file.(l) Their incisors are grooved with a longitudinal 

 furrow, and the tail is hairy, as well as the ears, which are large. 



O. capensis, Fred. Cuv. (The Cape Otomys.) Size of a Rat ; 

 fur marked with black and fawn coloured rings ; tail a third 

 shorter than the body. (2) 



Dipus, Gm. 



The Jerboas(3) have nearly the same kind of teeth as the true 

 Rats, except that there is sometimes a very small one immediately 

 before the upper molars. The tail is long and tufted at the end ; 

 the head large ; the eyes large and prominent j but their principal 

 character consists in their posterior extremities, which, in compari- 

 son with the anterior, are of a most immoderate length, and above 

 all, in the metatarsus of the three middle toes, which is formed of 

 one single bone, resembling what is called the tarsus in Birds. It 

 is from this disproportion of the limbs that they were named by the 

 ancients Biped Rats, and in fact they seldom move otherwise than 

 by great leaps on their hind feet. There are five toes to each of the 



(1) They are exact models, in miniature, of the gnnders of the Elephant. 



(2) It is the same animal described and represented in the essay on the g"enus 

 of Rats, by M. Brantz, Berlin, 1827, under the name oi Euryotis irrorata. 



(3) There has lately appeared an excellent paper on the Jerboas, by M. Lich- 

 tenstein, In which that learned naturalist describes and figures ten species. I 

 can only refer my readers to the paper itself. It is inserted in the Journal of 

 the Acad, of Berlin. 



