RODENTIA. 91 



species which have cheek-pouches like the Hamsters, and pass their lives 



in subterraneous holes, the Tamia of llViger. For instance the 



Sc. sfriafus, L. (The Ground Squirrel.) Which is found throughout 

 all the north of Asia and America, particularly in the pine forests. The 

 tail is more scantily supplied with hairs tlian tluit of the European Squirrel; 

 the ears smooth, and skin brown, with five black stripes and two white 

 ones. 



We ought also, most probabh^, to distinguish the Guerlinguets, a species 

 with a long, and almost round tail. 



They are found in both continents. 



The following have been separated already. 



Pteromts.(I) 



Or the Flying Squirrels, to which the skin of the flank, extending be- 

 tween the fore and hind legs, imparts the faculty of supporting themselves 

 for a moment in the air, and of making very great leaps. There are long 

 bony appendages to their feet, which support a part of this lateral mem- 

 brane. 



There is a species in North America. 



Sc. voluccella, L. (The American Flying Squirrel.) Reddish-grey above; 

 white beneath; size less than that of the preceding; tail three-fourths as 

 long as the body. It lives in troops in the prairies of North America. 



M. GeofFroy has very properly separated from this genus the 



Cheiho»ts.(2) 



Or the Aye-Ayes, whose inferior incisors, much more compressed, and 

 above all, more extended from front to back, resemble ploughshares. 

 Each foot has five toes, of which four of the anterior are excessively elon- 

 gated, the medius being moi'C slender than the others; in the hind feet the 

 thumb is opposable to the other toes; so that they are in this respect among 

 the Rodentia, what the Opossums are among the Carnaria. The structure 

 of their head is otherwise very different from that of the other Rodentia, 

 and is related to the Quadrumana in more points than one. 



There is only one species of the Aye-Aye known. It was discovered at 

 Madagascar by Sonnerat. It is the Cheir. madagascariensis. (The Aye- 

 Aye.) Size of a Hare, of a brown colour, mixed with yellow; tail long and 

 thick, with stout black bristles; ears large and naked. It is a nocturnal 

 animal, to which motion seems painful; it burrows under ground, and uses 

 its slender toe to convey food to its mouth. 



Linnaeus and Pallas united in one single group, under the name of 



Mus, Lin. 

 All the Rodentia furnished with clavicles, which they could not distinguish 



(1) Pteromys, Winged Rat. 



(2) Cheiromys, a rat with hands. 



