KEY TO THE ORDERS AND FAMILIES 
REPRESENTED WITHIN OUR LIMITS. 
KEY TO THE ORDERS. 
1. Fingers greatly elongated, supporting a leathery membrane which serves as a 
wing. Order CHIROPTERA, p. 445. 
2. Fingers not greatly elongated and not supporting a leathery membrane which 
serves as a wing. 
A. Feet provided with hoofs. Order UNGULATA, p. 57. 
B. Feet provided with claws or nails. 
br. No canine teeth present; a wide gap between cheek teeth and incisors; 
front teeth (incisors) large and chisel-shaped, never more than two 
in lower jaw. Order GLIRES, p. 97. 
bz. Canine teeth present and prominent, longer and noticeably different 
from the others. 
Tail and ears nearly or quite naked (hairless); female with external 
abdominal pouch. Order MARSUPIALIA, p. 49. 
Tail and ears not naked; female without abdominal pouch. 
Order FERA, p. 275. 
b3. Canine teeth present but not prominent and but little different from 
others; teeth continuous, with no wide gap between them; upper lip 
projecting beyond lower; snout long. Order INSECTIVORA, p. 405 
KEY TO THE FAMILIES. 
GROUP 1. Order MARSUPIALIA. Pouched Mammals. 
Tail nearly naked; ears naked; 
general color grayish white; teeth 
50; canine teeth present; hind foot 
with five toes, the innermost one 
shaped like a thumb and without 
claw; female with external abdom- 
inal pouch for carrying young after birth. A single species occurs within 
our limits, which is about the size of a large Domestic Cat. 
Family DIDELPHIIDZ. Opossums, p. 51. 
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