OF THE SPERM WHALE. 
93 
jaws, as the porpoise and grampus ; in others they are 
only in one jaw, as the spermaceti whale ; and in the 
large bottle-nose, described by Dale, there are only two 
small teeth in the anterior part of the lower jaw. In 
the nar- whale only two tusks in the forepart of the 
upper jaw, while in some others there are none at all. 
The teeth are not divisible into different classes, as in 
quadrupeds, but are all pointed teeth, and are commonly 
a good deal similar. Each tooth is a double cone, one 
point being fastened in the gum, the other projecting ; 
they are, however, not all exactly of this shape. In 
some species of porpoise the fang is flattened, and thin 
at its extremity. In the spermaceti whale, the body of 
the tooth is a little curved towards the back part of the 
mouth — this is also the case with some others. The 
teeth are composed of animal substance and earth, similar 
to the bony part of the teeth in quadrupeds. The upper 
teeth are commonly worn down upon the inside- — the 
lower, on the outside; this arises from the upper jaw 
being in general the largest. The situation of the teeth 
when first formed, and their progress afterwards, as far 
as T have been able to observe, is very different in 
common from those of the quadruped. In the quadruped 
the teeth are formed in the jaw, almost surrounded by the 
alveoli or sockets, and rise in the jaw as they increase in 
length, the covering of the alveoli being absorbed, — they 
afterwards rise with the teeth, covering the whole fang; 
but in this tribe the teeth appear to form in the gum 
upon the edge of the jaw, and they either sink in the jaw as 
they lengthen, or the alveoli rise to enclose them ; this last 
