GASTRIC TEETH. 



149 



Among the many instances in which teeth are 

 converted to uses widely different from mastication, 

 may be noticed that of the Squalls pristis, or Saw- 

 fish, where the teeth are set horizontally on the two 

 lateral edges of the upper jaw, which is prolonged 

 in the form of a snout (seen in a, Fig. 293), obviously 



-<rrrr^^ 



constituting a formidable weapon of offence, b is 

 a more enlarged view of a portion of this instru- 

 ment, seen from the under side. 



'§ 5. Trituration of Food in Internal Cavities. 



The mechanical apparatus, provided for triturating 

 the harder kinds of food, does not belong exclu- 

 sively to the mouth, or entrance into the alimentary 

 canal ; for in many animals we find this office per- 

 formed by interior organs. Among the inferior 

 classes we meet with examples of this conformation 

 in the Crustacea, the MoUusca, and above all in 

 Insects. Thus there is found in the stomach of the 

 Lobster, a cartilaginous framework, in which are 

 implanted hard calcareous bodies, having the form, 

 and performing the functions of teeth. They are 



