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 Muride: 
I. Meadow Mice, Lemmings and Muskrats 
(Sub-Family Microtine) 
Thick-set, short-legged, short-eared, short-tailed, 7. ¢. tail less 
than one-third the length of head and body (except muskrats) 
usually much less, mainly burrowers. 
Il. American Long-tailed Mice and Rats 
(Sub-Family Cricetine) 
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 Murine) 
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. 
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