66 COMPARATIVE ZOOLOGY. 
those nearer the lips. The teeth of Mammals only have 
fangs. 
The teeth of Fishes present the greatest variety. In 
number, they range from zero to hundreds. The Hag-fish 
(Myxine) has a single tooth on the roof of the mouth, and 
two serrated plates on the tongue; while the mouth of the 
Pike is crowded with teeth. In the very lowest of the 
class, we find teeth, short and blunt, in the shape of cubes, 
or prisms, arranged like mosaic work. Such pavement- 
teeth (seen in some Rays) are fitted for grinding sea-weed 
and crushing shell-fish. But 
the cone is the most common 
form: sometimes so slender 
and close as to resemble 
plush, as in the Perch; or of 
large size, and flattened like 
a spear-head with serrated 
Fig. 30.—Jaws and Pavement-teeth of edges, as in the Shark 5 but 
a Ray (Myliobates). more often like the canines 
of Mammals, curved inward to fit them for grappling. 
In the Shark, the teeth are confined to the fore part of the 
mouth; in the Carp, they are all situated on the bones of 
the throat; in the Parrot-fish, they occupy both back and 
front; but in most Fishes, the teeth are developed also on 
the roof, or palate, and, in fact, on nearly every bone in 
the mouth. They seldom appear (as in the Salmon) on 
the upper maxillary. As to mode of attachment, the teeth 
are generally anchylosed (fastened by bony matter) to the 
bones which support them, or simply bound by ligaments, 
as in the Shark. In a few Fishes, the teeth consist of 
flexible cartilage; but almost invariably they are com- 
posed of some kind of dentine, enamel and cement being 
absent. 
Of Reptiles, Toads, Turtles, and Tortoises are toothless; 
Frogs have teeth in the upper jaw only; Snakes have a 
