148 RATS, MICE, AND VOLES 



almost at your feet and nibble the stems of the succu- 

 lent grasses, just as his powerful relative the beaver 

 once gnawed tree-stems in this Itchen valley. The 

 truth is, the water-rat is not a rat (Mus) at all, but a 

 vole (Arvicola), the only true water-rat being found in 

 Australia (Hydromys). The voles may be distinguished 

 from rats and mice by several external marks, such as 

 blunt instead of pointed snouts, short instead of long 

 tails, stumpy ears and small eyes. But the most im- 

 portant difference is in the teeth ; the peculiar structure 

 of its molars, which have been pronounced the per- 

 fection of molar dentition, ought to exonerate the 

 water-vole for ever from all suspicion of eating spawn, 

 fish, or other perquisites of greedy man. The twelve 

 molars have no roots, but grow on endlessly like the 

 incisors of other rodents, supplying the constant wear 

 caused by gnawing. They are tubes of hard enamel, 

 corrugated longitudinally, filled with soft material. 



Out of about forty known species of vole, three 

 inhabit the British isles, namely, the water-vole 

 (Arvicola amphibius) ; the field- vole (A. agrestis), which 

 is the pest that occasionally multiplies inordinately and 

 destroys immense tracts of pasture and young woods ; 

 and the bank- vole (A. glareolus,} dignified by some 

 naturalists as a separate genus, because its characteristic 

 vole molars sometimes alter with age, the pulp cavities 

 hardening, and regular roots forming. 



It cannot be too widely known that anybody killing 

 a water-vole is destroying a perfectly harmless animal. 



