QUADRUPEDS. 189 



tions than in the preceding tribes ; it is indeed nearly 

 smooth. 



1. Summits of the grinders, with'conical processes, cover- 

 ed with enamel. The species subsist on animal food, or are 

 omnivorous. 



Incisors with pointed summits. 



Hind feet palmated. 



62. HYDROMYS. The summits of the grinders are ob- 

 liquely quadrangular > with a spoon-shaped hollow. H. leu- 

 cogaster of GEOFFROY. 



Hind feet simple. 



(A.) Three grinders in each jaw. 



With cheek-pouches. 



63. CRICETUSV Hamster. Tail short and hairy. Mus 

 cricetus, LIN. 



Without cheek-pouches. 



64. DIPUS. Jerboa. Tail long, ending in a bush. 

 Hind-legs remarkably long, so that the animal moves by 

 leaping. Musjaculus, LIN. 



65. Mus. Tail nearly naked. Hind legs of moderate 

 length. This restricted genus includes the common mouse 

 and rat. 



(B.) Five grinders on each side above, and four below. 



66. ARCTOMYS. Marmot. Social, becoming torpid. 

 Mus marmota, LIN. 



Incisors with chisel-shaped summits; the Dentes seal- 

 prarii of GREW. 



Grinders three on each side in both jaws. 



67. SPALAX. Zemni. Fives toes before and behind, 



