FISHES. 



259 



Teeth, which are so characteristic of Vertebrata, are 

 nowhere found in such variety of form and function as 

 among Fishes. They are not confined to the jaws, but 

 are found by turns in almost every one of the bones that ■* 

 compose the mouth, though not in all species. They are 

 generally simple spines, curved backwards; but innume- 

 rable modifications of this form occur. Thus the jaws of 

 the deadly Shark are flat and lancet-like, the cutting 

 edges being notched like a saw; the front teeth of the 

 Plaice and the Flounder are compressed plates ; some, as 

 the Wrasse, have flat grinding teeth; others, as the 

 Sheep's-head, have the grinding surface convex ; and 

 others, as the genus Chrysophrys, have convex teeth so 

 numerous and so closely packed over a broad surface, as 

 to resemble the paving-stones of a street. The beautiful 

 Chsetodons of warm climates, on the other hand, have 

 teeth which resemble bristles, and these are set close to- 

 gether like the hairs of a brush ; while the Perch of our 

 own rivers has them still more slender, minute, and nume- 

 rous, so as to resemble the pile of velvet. Another of 

 our well-known fishes, the bold and fierce Pike, is armed 

 with teeth scarcely less formidable in size, form, and sharp- 

 ness, than the canines of a carnivorous quadruped. In 

 number, also, there is a great variety. The Pike, the 

 Perch, the Cat-fish, and many others, have the mouth 

 crowded with innumerable teeth, while the Carp and the 

 Roach have only a few strong teeth in the throat, and 

 a single flat one above ; and the Sturgeon, the Pipe-fish, 

 and the Sandlaunce, are entirely toothless. 



The eye in this Class presents a beautiful example of 

 adaptation to the medium in which they live. From the 



