RODENTIA. 



115 



proji-ess, they devastate the country through which tney pass. Their ordinary residence appears to be the shores 

 of the Arctic Ocean. 



The Siberian Lemming, or Zocor (A/k« 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 diiTerent LiUacea. 



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 (Miis Hiidsonicus, 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 Otomvds {Otomys, F. Cuv. ; [Eurt/otis, Brandt] ) — 

 Are nearly allied to the Voles, and have also three grinders, but composed of slightly arcuated laminEe, 

 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. 



The only known species, the Cape Otomyd (O. 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 (Dipus, Gm.) — 

 Have nearly the same teeth as the Rats properly so called, diflfering only in the occasional presence of 

 a very small tooth, placed before the superior molars. Theii- 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 bone, as in what is termed the tarsus of birds. Tliis 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 live in burrows, and become profoundly toi-pid in winter. 



[There are numerous species, inhabiting Asia and Africa. Tliose with five toes have been brought together by 

 some under the name Aleciaga.] 



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 tiie 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 termmated by large claws almost 

 resembling hoofs. The nimiber of their 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 (Miis caffer, Pallas ; Dipus caffer, 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 (Spalax, Guldensteiit) — 

 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 lips, and the extremities of those of the lower jaw 



* Tlic Plovers, and scleral otlter birds belonging; to the lanl? ^oup, present a somewhat analogous conformation. — Kn. 



I 2 



