OF CREATION. 



163 



aquatic crocodiles of the present day. The jaws 

 are long, comparatively slender, and tapering to the 

 extremity. Along their whole length on both sides 



Fig. 59 



ICHTHYOSAURUS. 

 (Side View of the Skull.) 



there is a continuous row of conical teeth of large 

 size, not inserted in separate sockets, but placed in a 

 kind of trough cut in the jaw, and merely separated 

 from one another by a ridge of bone. These teeth 

 were constantly removed and replaced by new ones 

 during the whole life of the animal. 



The structure of the lower jaw indicates a mecha- 

 nical contrivance of some interest, intimately con- 

 nected with the wants and habits of the animal. 

 The jaws themselves are, as we have seen, long and 

 slender. The teeth show that the animal was fierce 

 and voracious, and analogy teaches us that in such 

 cases the jaws must close suddenly on their prey with 

 a snap, in order to ensure a proper hold being ob- 

 tained. But a slender lower jaw, however strong, 

 would be very easily broken when brought in con- 

 tact with hard bodies, such as the solid enamelled 

 plates enclosing some of the fish of the liassic period. 

 By a complicated apparatus of several pieces of bone, 



