58 REPORT OF NEW JERSEY STATE MUSEUM. 
Odocoileus americana Rhoads, Mam. of Pa. and N. J., 1903, 
Dp: 24. 
Dorcelaphus virgimanus Rhoads, Proc. Acad. Nat. Sci. Phila., 
1897, p. 25. 
Order GLIRES. 
Gnawing Mammals. 
Here belong our rats, mice, squirrels, rabbits, etc., all of 
which agree in a remarkable arrangement of the teeth, which at 
once separates them from all other mammals. ‘The incisors 
or front teeth, two in each jaw, are curved and grow continu- 
ously from the’ base, as their edges wear away from rubbing 
against each other during the process of gnawing, which is car- 
ried on in precisely the same way whether it be the house mouse 
making inroads into our cheese, or the beaver cutting down forest 
trees for his dam. 
There are no canine teeth at all in the rodent’s jaws and a 
broad gap extends from the incisors to the flat topped grinders, 
or molars, set close together, four on each side in the back of 
the mouth. Rodents are for the most part small animals with 
short legs and sharp claws on the toes. They are represented by 
numerous species, widely distributed and adapted for all kinds 
of life, terrestrial, fossorial, arboreal, erial and aquatic. The 
several families to which our New Jersey species belong, may be 
distinguished as follows: 
a. A pair of small rudimentary incisor teeth situated behind the large ones 
in the upper jaw. LEPORIDAE (Rabbits.) 
aa. No rudimentary incisors. 
b. Hair thickly interspersed with sharp spine like quills. 
ERETHIZCNTIDA (Porcupines. ) 
bb. No spines present. 
c. Lower leg bones (tibia and fibula) fused together at the lower 
ends; Mouse ‘Tribe. 
d. Hind legs long, tail longer than head and body. 
ZAPODIDA (Jumping Mice.) 
dd. Hind legs short, tail not exceeding the head and body. 
MURIDA (Mice and Rats.) 
cc. Lower leg bones free. Squirrel Tribe. 
e. Tail broad and flat, naked. CASTORIDH (Beavers.) 
ee. Tail normal, bushy. sciuRIDA (Squirrels.) 
