114 



ANIMAL BIOLOGY 



body surface by several gill slits, and by a skin roughened by 

 small tooth-like projections. 



Sharks are confined to marine waters and are most abundant 

 in the tropics. The most common species off our coasts are the 



A ^ — ^ ^==— - -^ B 



Fig. 70. — A, Sting Ray, Stoasodon narinari; B, Eagle Ray, Myliobalis 

 aquila. (From Newman, after Jordan and Evermann, and Bridges.) 



small Dogfish Sharks, notorious pests to fishermen but favorites 

 for dissection in zoological laboratories. (Figs. 69, 120.) 



Whereas the Sharks have the typical stream-line body of swift 

 swimmers, the Rays, or Skates, are bottom-dwellers, and have a 



Operculum 



Fig. 71. — Mackerel, Scomber scombrus. 



greatly flattened body with eyes on the dorsal, and mouth and 

 gill slits on the ventral surface. The most famous of the Rays are 

 the Torpedoes, so-called because they are able to give a severe 

 electric shock. (Fig. 70.) 



