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 Liliacez. 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. hudsonius ; Mus hudsonius, Gm., Schreb. CKCVI. (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 unknown, except in 
this animal. It is the size of a Rat, and lives under ground in 
North America. 
Oromys, Fred. Cuv. 
The Otomys are nearly allied to the Field Rats, and have also 
three grinders, but they are composed of slightly arcuated laminz 
arranged in file.(1) Their incisors are grooved with a longitudinal 
furrow, and the tail is hairy, as well as the ears, which are large. 
O. capensis, Fred. Cuy. (The Cape Otomys.) Size of a Rat; 
fur marked with black and fawn coloured rings; tail a third 
shorter than the body.(2) 
Direus, 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 5 
the head large; the eyes large and prominent ; 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 grinders of the Elephant. 
(2) It is the same animal described and represented in the essay on the genus 
of Rats, by M. Brantz, Berlin, 1827, under the name of 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. : 
i | Nt 
ere 
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