FISHES. 



323 



to a great extent, since no other forms give such a clear 

 understanding of the characters of the group. Of the 

 several orders, only the Squall, Raise, and Holocephali 

 need mention here. 



ORDER I. SQUALI (Sharks). 



In the sharks the body is more or less cylindrical, and 

 the gill-slits open upon the sides of the neck. About 150 



FIG. 122. Sawfish 

 (Pristis pectinatus). 

 After Goode. 



FIG. 123. Common Skate (Raia erinacea). 



species are known, some, like the dogfish, being small, 

 others reaching an enormous size. Those species which 



