Rats, Mice and Lemmings 



stitute satisfactory groups in which to classify our species. The 

 latter, however, are divisible into two very natural assemblages 

 which we might term the short-tailed and long-tailed groups. 



The former are thick-set, short-legged and short-eared, with 

 a very short tail, small eyes and thick fur. All of which charac- 

 ters stamp them as burrowing animals. 



The long-tailed group, on the other hand, are sleek and 

 graceful, standing higher on their legs, with usually large ears, 

 big eyes and a long slender tail. 



We frequently find that it is impossible to properly classify 

 animals by external characters alone, and so in this case we find 

 the muskrat excluded from the first group where he belongs 

 by his long tail, but after noting this exception we may adopt 

 the characters as satisfactory without considering the more fun- 

 damental peculiarities of teeth and skull upon which science relies. 

 We have then three groups of the Muridce: 



I. Meadow Mice, Lemmings and Muskrats 



(Sub-Family Microtina) 



Thick-set, short-legged, short-eared, short-tailed, i. e. tail less 

 than one-third the length of head and body (except muskrats) 

 usually much less, mainly burrowers. 



II. American Long-tailed Mice and Rats 



(Sub-Family Cricetince) 



More slender, with longer legs and generally larger ears and 

 eyes and long tail, the latter always more than half the length 

 of the head and body, generally much more. 



III. Introduced Mice and Rats 



(Sub-Family Murince) 



Resembling in a general way the last group, but with very differ- 

 ent skull and teeth. All natives of the Old World, whence they have 

 been brought by man. 



106 



