HIGH SCHOOL ZOOLOGY. 



77 



Fig. 53.— The Torpedo or Electric Ray. Torpedo occidentalis. ^. 

 (U. S. F. C.) 



the Electric Rays (Torpedo) (Fig, 53) are singular in that the 

 muscles of the pectoral fin ax'e largely converted into an electric 

 organ. The Sharks (Fig. 54) are all carnivorous and voracious 



Fig. 54.— The Homed Dog Fish. Squalus acanthias. I. 

 (U. S. F. C.) 



forms of great strength and activity ; some of the smaller ones 

 (Mustelus) live on Shell-fish, but the largest species are often 

 dangerous to man and attain a length of thirty to forty feet 

 (Carcharodon, Selache). In all the Sub-Class the skeleton is 

 cartilaginous, and the skin either smooth or roughened with 

 minute teeth which are similar in structure to the more for- 

 midable teeth of the jaws. They resemble the Ganoids in 

 the structure of the heart and intestine, and in the unequal 



