BRITISH ARVICOL^E, OR VOLES. 99 



examined several black and brown specimens taken 

 in various localities, and will proceed to point out 

 what I consider to be the actual distinction between 

 them. 



In the first place, the black kind is considerably 

 the smaller of the two, a full-grown specimen of the 

 common sort averaging thirteen inches in total 

 length, whereas the other rarely exceeds nine ; 

 secondly, the tail is, in all cases that have come 

 under my personal notice, considerably longer in 

 the black vole. The head is also smaller, and the 

 eyes smaller in proportion to the size of the animal. 

 On dissection, the only distinction I could find was 

 that the principal intestine was considerably larger, 

 when extended, in the black specimens. There was 

 no difference in dentition, but the form of the skull 

 was proportionately more lengthened in the black 

 than in the brown individuals. I have seen young 

 specimens of both varieties, but have never met 

 with a black specimen inhabiting the same burrows 

 with the brown ones, but always appearing to form 

 a small colony of their own. Indeed, I believe that 

 several species of our smaller mammalia are con- 

 founded together or imperfectly known, especially 

 among the bats, shrews, and rodents. 



The second species that comes under our notice 

 is the field-vole (Arvicola campestris). This species 

 is considerably smaller than the water-vole, seldom 



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