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GENUS ARVICOLA.— Lacepeue. 



DENTAL FORMULA. 



Ijicisive 2; Canine j^; Molar g^ = 16. 



Incisors, in the upper jaw, large and cuneiform ; in the inferior jaw, 

 sharp. 



Molars, compound, flat on their crowns, the enamel forming angular 

 ridges on the surfase. 



Fore-feet, having the rudiments of a thumb, and four toes, furnished 

 with weak nails. 



Hind-feet, with five toes, hairy on their borders, armed with claws. 



Ears, clothed with hair ; tail, cylindrical and hairj, shorter than the 

 body. From eight to twelve pectoral and ventral mammae. 



The old family of Mus has undergone many subdivisions. It formerly 

 included many of our present genera. The Arvicolse, by the structure of 

 their teeth, and the hairy covering of their ears and tail, the latter being 

 besides short, may advantageously be separated from the rest. 



They burrow in the earth, and feed on grain, bulbous roots and grasses ; 

 some are omnivorous, they do not climb, are not dormant in winter, but 

 seek their food during cold weather, eating roots, grasses, and the bark 

 of trees. 



There have been about forty species of Arvicola described ; some of 

 these, however, are now arranged under other genera. Some of the 

 species are found in each quarter of the world, about seven species 

 inhabit North America. 



The generic name is derived from two Latin words, arvus, a field, and 

 colo, I inhabit. 



