RODENTIA. 115 



pro^cress, they devastate the country throii^^h whicli tney pass. Tlieir ordinary residence appears to be the shores 

 of tlie Arctic Ocean. 



The Siberian LemmiriEi-, or Zocor fjl/«jr a.spalax, Gni.)— T^cddish-j^rey ; the three middle nails of the fore-feet 

 loni;-, arcuated, compressed and trenchant, fcr cutting; earth and roots. The limbs are short; there is scarcely 

 any tail ; and the eyes are exceedinc:ly small. From Siberia, -vvbere it lives uuder-g-ruund, bke the Moles and 

 Mole-rats, and subsists chiefly on the bulbs of dilTerent L/liacccc. 



The third species, like the other animals comprehended under the c;reat j^emis 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-g'rey 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 lari^e as a Rat, and lives under ground in North 

 America. 



The Otomyds {Oioniys, F. Cuv. ; [Enri/ofts, Brandt] ) — • 

 Are nearly allied to the Voles, and have also three grimlcrs, hut 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 

 heing also large. 



Tlie only known species, the Cape Otomyd (0. cnpensif:, F. Cav.). ijibabits Africa, and is of the size of a Rat, 

 with fur annulated black and fulvous. Tail a third shorter than the body. 



The Jerboas (BIjjus, Gm.) — 

 Have nearly the same teeth as the Kats properly so called, differing only in the occasional presence of 

 a \ery 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, wliich is formed of a single hone, as in what is termed the tarsus of birds. This dispro- 

 portion of the limbs caused them to he designated iwo-footod }\ais 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 Uve 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 AJectaga.} 



The IIelamyds {Helamys, F. Cuv. ; Pedetes, 111.), — 

 AVhich 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 lamina; ; live 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 their toes is accordingly inverse to that of the ordinary Kats. 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 {Mas cafftr, Pallas ; Dipii^s coffer y Gm.)— It inha- 

 bits deep burrows near the Cape of Good Hope. 

 [Tlie affinities of this curious animal are by no 

 means obvious.] 



The JIole-rats {SpaJax, Guldenstedt) — 

 Have also been very properly separated from 

 the genus of Rats, although their grinders are 

 three in number, and tuberculaled 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 he covered hy the hps, and the extremities of those of the lower jaw 



* Till' I'lnvfi-s, iukI s- crjil oilicr birils bclorffiiiuf to tlic fiiijiie ljoviii, prcst'iil a souic«li:it fixKa-ic-oiis conroriiiritiori.— f,t,. 



I '2 



