244 TEETH OF THE WOLF-FISH. 



hoops or arclies supporting the gills, and sorae have them 

 developed from the bone of the nose and the base of the 

 skull. In the carp and tench the teeth are confined to 

 this latter unusual position, and to a pair of bones, called 

 "pharyngeal," which circumscribe the back outlet of the 

 mouth. 



Fishes exhibit, moreover, a greater range of variety in 

 the mode of attachment of the teeth than any other class 

 of animals. In the sharks, and the singular fish called 

 the "angler," the teeth are movable, their base being tied 

 by ligaments to the jaw. In the angler the ligaments are 

 so inserted that they do not permit the teeth to be bent 

 outwards beyond the vertical position, but yield to pres- 

 sure in the contrary direction, by which the point of the 

 tooth may be directed towards the back of the mouth; 

 the instant, however, that the pressure is remitted, the 

 tooth returns through the elasticity of the bent ligaments, 

 as by the action of a spring, to its usual erect position; 

 the deglutition of the prey of this voracious fish is thus 

 facilitated, and its escape prevented. The broad and 

 generally bifurcate bony base of the teeth of sharks is 

 attached by ligaments to the semi-ossified crust of the 

 cartilaginous jaws; but they have no power of erecting 

 or depressing the teeth at will. 



The teeth of the sphyr^ena are examples of the ordinary 

 implantation in sockets, with the addition of a slight an- 

 chylosis of the base of the fully-formed tooth with the 

 alveolar walls; and the compressed rostral teeth of the 

 saw-fish are deeply implanted in sockets; the hind 

 margin of their base is grooved, and a corresponding 

 ridge from the back part of the socket fits into the groove, 

 and gives additional fixation to the tooth. 



The singular and powerfully developed dental system 



