A KEY TO THE GENERA OF NORTH 
AMERICAN MAMMALS 
Animals are classified scientifically into groups of different 
rank, known as orders families and genera, and the technical 
mame of any species consists of the name of the genus to 
which it belongs, coupled with its own individual specific name. 
If it shows definite variations in size, colour, etc., in different 
parts of its range, these geographic races are indicated by a 
third or sub-specific name. 
In the preceding pages the inammals have been arranged 
by orders and families in their natural sequence, and the char- 
acters of these larger groups explained. Inasmuch as a large 
number of the genera of American mammals are represented in 
our limits by but a single species, it was not deemed advisable 
in a work of this kind to treat the several genera and the more 
minute characters upon which they are based under separate 
headings, especially as many of the generic characters are given 
in the descriptions of the species. 
In order, however, to facilitate the identification of any 
mammal which the reader may have in hand, the following key 
has been prepared by which it may be traced to its genus, 
while the page numbers following refer directly to the body of 
the book where the descriptions of the several species may be 
found. In this key the most obvious generic characters are 
contrasted and the dentition of each genus is given. In stating 
the dental formula it will be understood that the figures indicate 
the number of teeth on one side of the jaws only, the number 
above the line referring to the upper jaw, that below to the 
lower; the letters indicate: 7, incisors, ¢, canines, ~, premolars, 
m, molars. 
Only genera treated in the foregoing pages are included, 
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