248 TEETH OF THE BARRACUDA FISH. 



polypes and their cells are reduced to a pulp by the action 

 of the pharyngeal jaws and teeth that close the posterior 

 aperture of the mouth. 



There is a close analogy between the dental mass of 

 the scarus and the complicated grinders of the elephant, 

 both in form, structure, and in the reproduction of the 

 component denticles in horizontal succession. But in the 

 fish, the complexity of the triturating surface is greater 

 than in the mammal, since, from the mode in which the 

 wedge-shaped denticles of the scarus are implanted upon, 

 and anchylosed to, the processes of the supporting bone, 

 this likewise enters into the formation of the grinding 

 surface when the tooth is worn down to a certain point. 



The proof of the efl&cacy of the complex masticatory 

 apparatus above described, is afforded by the contents of 

 the alimentary canal of the scari. Mr. Charles Darwin, 

 the accomplished naturalist and geologist, who accompa- 

 nied Captain Fitzroy, E. N"., in the circumnavigatory 

 voyage of the Beagle, dissected several parrot-fishes 

 soon after they were caught, and found the intestines 

 laden with nearly pure chalk, such being the nature of 

 their excrements; whence he ranks these fishes among 

 the geological agents to which is assigned the office of 

 converting the skeletons of the lithophytes into chalk. 



The most formidable dentition exhibited in the order of 

 osseous fishes is that which characterizes the sphyr^na, 

 and some extinct fishes allied to this predatory genus. 

 In the great barracuda of the southern shores of the 

 United States {SphyrcBna harracuda^ Cuv.), the lower-jaw 

 contains a single row of large, compressed, conical, sharp- 

 pointed, and sharp-edged teeth, resembling the blades of 

 lancets, but stronger at the base ; the two anterior of 

 these teeth are twice as long as the rest, but the posterior 



