246 



VERTEBBATA. 



vaticits), hamster ( Cricetus frumentarius), jerboa (Dipus sagitta), 

 dormouse (Myoxus avellanarius), water-rat or vole (Arvicola am- 

 phibius), field-mouse (Arvicola agrestis), beaver (Castor fiber], 

 prairie-dog (Cynomys ludovicianus), marmot (Arctomys marmota), 

 and squirrel (Sciurus vulgaris}. 



Alston divides the Eodentia into three suborders, according to 

 the characters of the teeth ; one of these is subdivided into three 

 sections : these are indicated in the following list : 



