RODENTIA. 
115 
progress, they devastate the country through which they pass. Their ordinary residence appears to be the shores 
of the Arctic Ocean. 
The Siberian Lemming, or Zocor {Mus aspalax, Gm.)— Reddish-grey ; the three middle nails of the fore-feet 
long, arcuated, compressed and trenchant, for cutting earth and roots. The limbs are short ; there is scarcely 
any tail ; and the eyes are exceedingly small. From Siberia, where it lives under-ground, like the Moles and 
Mole-rats, and subsists chiefly on the bulbs of different LiUacece. 
The third species, like the other animals comprehended under the great genus of Rats, has only the rudiment 
of a thumb to its fore-feet. It is the Hudson’s Bay Lemming (Mus Hudsonicus, Gm.) ; of a pearl-grey colour, 
without any tail or external ears: the two middle toes of the fore-feet of the male seem to have double 
claws, the skin at the end of the toe being callous, and projecting from under the nail ; a variety of con- 
formation unknown except in this animal.* It is as large as a Rat, and lives under ground in North 
America. 
The Otomyds {Otomys, F. Cuv. ; [_Euryotis, Brandt] ) — 
Are nearly allied to the Voles, and have also three grinders, but composed of slightly arcuated laminae, 
which are arranged successively in file, so as to present an exact miniature resemblance to the grinders 
of the Elephant. Their incisors are grooved longitudinally, and the tail and ears are hairy, the latter 
being also large. 
Tlie only known species, the Cape Otomyd (0. capensis, F. Cuv.), inhabits Africa, and is of the size of a Rat, 
with fur annulated black and fulvous. Tail a third shorter than the body. 
The Jerboas {Bipus, Gm.) — 
Have nearly the same teeth as the Eats properly so called, differing only in the occasional presence of 
a very small tooth, placed before the superior molars. Their tail is long and tufted at the end, the 
head large, and eyes large and prominent ; but their principal character consists in the immoderate 
length of the hinder limbs, as compared with the anterior, and above all, in the metatarsus of the three 
middle toes, which is formed of a single hone, as in what is termed the tarsus of birds. This dispro- 
portion of the limbs caused them to be designated two-footed Rats by the ancients : and in fact their 
ordinary gait is by great leaps on the hind-feet. Their fore-feet have each five toes ; and in certain 
species, besides the three great ones to the hind-feet, there are [one or two] small lateral toes. These 
rodents hve in burrows, and become profoundly torpid in winter. 
[There are numerous species, inhabiting Asia and Africa. Those with five toes have been brought together by 
some under the name Alectaga.'] 
The Helamyds {Helamys, F. Cuv. ; Pedetes, 111.), — 
Which are commonly termed Jumping Hares, have, like the Jerboas, the head large, as are also the eyes, a 
long tail, and very short fore-legs in comparison with the hinder ; the disproportion, however, being much 
less than in the true Jerboas. Their peculiar characters consist in having four grinders, each com- 
posed of two laminae ; five toes to the fore-feet, armed with long and pointed nails, and four only to 
the hind-feet, all separate, even to the bones of the metatarsus, and terminated by large claws almost 
resembling hoofs. The number of theii’ toes is accordingly inverse to that of the ordinary Rats. Their 
inferior incisors are truncated, and not pointed as in the Jerboas, and as in the majority of other 
animals which have been comprised in the great genus of Rats. 
One species only is known, as large as a Rabbit, 
and pale fulvous, with a long tufted tail black at the 
tip {Mus caffer, Pallas ; Bipus coffer, Gm.) — It inha- 
bits deep burrows near the Cape of Good Hope. 
[The affinities of this curious animal are by no 
means obvious.] 
The Mole-rats {Spdlax, Guldenstedt) — 
Have also been very properly separated from 
the genus of Rats, although their grinders are 
three in number, and tuberculated as in the 
Rats properly so called, and also the Hamsters, 
and are merely a little less unequal ; their in- 
cisors being too large to be covered by the 
* The Plovers, and several other birds belonging to the same group, present a somewhat analogous conformation. — E d. 
I 2 
Fig. 46.— Mole-rat. 
lips, and the extremities of those of the low^er jaw 
