344 



ZOOLOGY, 



food. Some species have no teeth ; but in most there exist 

 several rows, as in the shark (Fig. 315) ; we find them, 

 indeed, attached to several bones with which they unite, for 

 thev have no roots ; they are shed at regular intervals and 

 replaced by new teeth, and being generally all of one kind 

 they receive their names from the bones which carry them, 



Fig. 314. The Turbot. 



as palatine, vomerine, maxillary, &c. But in different species 

 they vary very much in form, being sometimes so fine and 

 thickly set as to resemble the pile of velvet, in others they 

 are strong robust hooks, rounded tubercles, or sharp cutting 



Fig. 315. Head of the Shark. 



486. Some, as the lamprey, live by suction, nevertheless 

 they also have teeth. There is no salivary apparatus, and 

 the gullet is short, the liver large and soft, and the pancreas 

 is replaced by the pancreatic caeca surrounding the pylorus : 

 finally, the position 6f the extremity of the gut varies much ; 

 the kidneys are extremely large, extending on both sides of the 



