208 CASTOKIDJE. 



RODENTIA. CASTORIDM. 



a, c, Nat. size. Kent's Hole. 



ARVICOLA PRATENSIS. Bank Vole. 



FOR the knowledge of this Vole, as a fossil of equal an- 

 tiquity with the preceding, I am indebted to Mr. Water- 

 house, whose special study of the osteology and dentition 

 of the Rodent quadrupeds, particularly qualifies him for 

 discriminating the nearly equal-sized and closely-allied spe- 

 cies of the present genus. The Bank-vole is distinguished 

 from the Field-vole, in addition to the characters pointed 

 out by Mr. Bell,* by the early addition of roots to the 

 molar teeth ; the crowns of these teeth are also narrower 

 in proportion to their antero-posterior extent, than in the 

 Armcola agrestis ; both this character, and the smaller size 

 of the jaws, are shown in the specimens figured above, 

 where b is a magnified view of the grinding surface of the 

 upper molars, and d that of the lower molars. They were 

 obtained by Mr. Mac Enery from Rentes Hole, and are 

 now in the British Museum. 



These remains of the Bank Vole carry back, more un- 

 equivocally, perhaps, than those referred to the Field-vole, 

 the date of these small and feeble Rodents to the remote 

 antiquity of the sera of the great extinct Cave-mammalia. 

 The existence of the little Bank-vole as a living member 

 of the British Fauna, was discovered by Mr. Yarrell, who 

 has described it under the name of Armcola 



* British Quadrupeds, p. 331. 



f- Proceedings of the Zoological Society, 1 832, p. 1 09. 



