CHAPTER V 

 THE TEETH OF FISHES 



The first and lowest class of the Vertebrates is 

 that of the Fishes. They are entirely aquatic in 

 their habits, and breathe by means of gills. The 

 body is bare, or covered with horny scales. The 

 limbs are modified into organs for swimming. 

 The nervous system is centralized in the spinal 

 cord, but there is little enlargement of the cephalic 

 portion. In the lowest forms, as the Amphyoxus, 

 there is no enlargement at all. The osseous 

 structures are soft and cartilaginous, and partake 

 of the general low structure of the class. The 

 vertebrae are cupped before and behind, except in 

 the Pike and some other forms which show a step 

 toward the reptilian character of being cupped in 

 front and balled behind. The jaws are often mov- 

 able and loose, and capable of protrusion and re- 

 trusion. 



The Teeth of Fishes. The true fishes have true 

 teeth. There are many kinds of teeth among the 

 many species of fishes, which are developed in 

 every conceivable position upon the various bones 

 and cartilages of the head. They are sometimes 



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