THE BEAVER AS A SPECIES 211 
peculiar feature of the head are the teeth, which 
are most wonderfully developed to meet the 
animal’s method of living. Their total number is 
twenty, ten in each jaw. These consist of eight 
molars or grinding teeth and two incisors for cut- 
ting. \These latter are the chisel-like teeth with 
which the beaver is able to cut down the great 
forest trees. In their construction they are of 
especial interest. The outside or front is a thin 
layer of very hard orange-coloured enamel attached 
Skeleton of Beaver. 
to a thick backing of dentine, which, being soft, 
wears away by the action of cutting and leaves the 
shell-like edge of enamel always sharp. The lower 
teeth are of great length, approximately four inches 
along the outer curve, of which a minimum of 
about one quarter extends beyond the jaw-bone. 
The incisors of the upper jaw are both shorter and 
more abruptly curved. The distance between 
these and the molars is about one-and-a-half times 
the space occupied by the groups of molars, 
These are curious rootless teeth composed of 
P2 
