208 CASTORID &®. 
RODENTIA. CASTORID 4. 
Fig. 78. 
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 
Arvicola agrestis ; both this character, and the smaller size 
of the jaws, are shown in the specimens figured above, 
where 6 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 Kent’s 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 era 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 Arvicola riparia.t 
* British Quadrupeds, p. 331. 
+ Proceedings of the Zoological Society, 1832, p. 109. 
