THE TRUE 



Virgin, off Block Island, was about seventy feet in length. 

 They are harmless, living upon small pelagic animals that 

 are strained into the throat through a series of hard, elastic, 

 whalebone-like fringes, that are arranged comb-like along 

 the large gill-openings. The teeth are small and compara- 

 tively useless. The Rhinodon (Fig. 199) is a similar form 

 of East African waters, and attains a length of sixty or 

 seventy feet. The mouth opens on a level with the snout 

 When struck, they have been known to carry large boats 

 beneath the surface. 



VALUE OF SHARKS. They are all scavengers. The skin of dog- 

 fish and others is used as leather and shagreen. The oil of nearly all 

 the species is valuable, and the bodies as guano. The teeth of sharks 

 are used as weapons by the Pacific islanders. In China the shark-fin 

 trade is an important one, they being used as food. 



Saw-Fishes (Prisfidte). These remarkable fishes 

 (Fig. 200) attain a length of fifteen feet, and are common 

 on th: North American coast from Cape Cod southward. 



TJr 



FIG. 200. Saw-fish. 



The snout is prolonged into a sword, the edges being 

 armed with sharp, bony teeth. A species of saw-fish lives 

 in a fresh-water lake in the Philippine Islands. The saw 

 is used as a weapon by some tribes. They are vivipa- 

 rous. 



Skates (Rauuda). These fishes are all notable for 

 the development of the side or pectoral fins that in some 

 species appear like wings. Their teeth are grinding plates, 

 adapted for crushing mollusks and crabs. Their eggs are 

 deposited in a dark, rectangular, parchment-like case, hav- 



