292 COMPARATIVE ANATOMY OF THE TEETH. 



mentary fangs. As many as eleven have been seen, so that 

 when one is shed there is another to take its place. 



All the frogs are said to have teeth in both jaws, and 

 all, with the exception of a single variety called the pipa, 

 have teeth in the roof of the palate. 



FOURTH CLASS FISHES, (PISCES.) 



Fish constitute the last class of the vertehrated division of 

 the animal kingdom. Their dental system presents great 

 variety, both in number and arrangement. The teeth are 

 found in all parts of the mouth and pharynx, and are distin- 

 guished, according to their situation, into intermaxillary, 

 mandibular, palatine, vomerial, lingual, bronchial, and pha- 

 ryngeal. 



The teeth of fish are either received into alveolar cavi- 

 ties, and are firm and immovable, or are removed from the 



maxillary bones, and have not 

 the cavities, as in the cartila- 

 ginous fishes, except the saw 

 fish, and are movable as in the 

 shark, which has the power of 

 elevating and depressing its 

 teeth. 



The fact of the teeth being 

 thus removed from the bone and 

 connected with mucous mem- 

 brane, is regarded as conclu- 

 sive in reference to the theory of their origin from mucous 

 membrane. 



The form of the teeth of fish is exceedingly various 

 some are conical, others flattened; the conical form the 

 largest number, and sometimes present a single point, at 

 others two or three points. In a variety called the scarius 

 there are five or six rows, composed each of five or six teeth 

 united by a species of cement. 



FIG. 81 represents the teeth of the Rock Fish, (labrus.) They are attached 

 to the inferior pharyngeal bone, are very numerous, are scattered over a broad 

 surface, and are said to resemble a * pavement." 



