92 MAMMALIA. 



by some very sensible external character, such as the tail of the Squirrel or 

 that of the Beaver, from which resulted the utter impossibility of assigning 

 to them any common character; the greater number had merely pointed 

 lower incisors, but even this was subject to exceptions. 



Gmelin has already separated from them the Marmots, Dormice, and the 

 Jerboas; but we carry their subdivisions much further, from considerations 

 founded on the form of their grinders. 



ARCTOMYS, Gm.(l) 



The Marmots, it is true, have the inferior incisors pointed like those of 

 the greater number of animals comprehended in the great genus Mus; but 

 their grinders, like those of the Squirrel, amount to five on each side above 

 and four below, all bristled with points; accordingly, some species are in- 

 clined to eat flesh and feed upon insects, as well as grass. There are four toes 

 and a tubercle in place of a thumb to the fore feet, and five toes to the 

 hind ones. In other respects these animals are nearly the direct reverse 

 of the Squirrels, being heavy, having short legs, a middle sized or short 

 hairy tail, and a large flat head, passing the winter in a state of torpor, 

 and shut up in deep holes, the entrance of which they close with a heap of 

 grass. They live in societies, and are easily tamed. Two species are 

 known in the eastern continent. One is 



Arct. alpinus. (The Alpine Marmot.) Large as a Hare; tail short; fur 

 yellowish grey, with ash coloured tints about the head. It lives in high 

 mountains, immediately below the region of perpetual snow. 



America also produces some species. 



Jlrct. monax, Buff. (The Maryland Marmot.) Grey; tail blackish, as 

 well as the top of the head. 



Jird. empetra, Pall. Less than the preceding; grey; red beneath. 



SPEHMOPHILUS, Fred. Cuv. 



We apply this name to those Marmots that have cheek pouches. The 

 superior lightness of their structure has caused them to be called Ground 

 Squirrels. Eastern Europe produces one species: 



Jl. citillus. (The Souslik or Zizel.) A pretty little animal, of a greyish 

 brown, watered or mottled with white, the spots very small, which is 

 found from Bohemia to Siberia. It has a peculiar fondness for flesh, and 

 does not spare even its own species. 



North America has several species of them, one of which is remarkable 

 by the thirteen fawn coloured stripes which extend along the back on a 

 blackish ground. It is the Thirteen striped Souslik, Arct. 13-lineatus, Harl.; 

 or Sciurus 13-lineatus, Mitchell; or Jlrct. Hoodii, Sabine. 



There is one of the Rodentia which it appears we must approximate to 

 the Marmots, that is remarkable for living in large troops in immense bur- 



Bear-Rat. 



