CARTILAGINOUS FISHES. 321 



of some of their members. Of the first we will cite only 

 the hippocampus or sea-horse, sometimes caught in our 

 bays and rivers, and of the second, the globe-fish, which 

 has a curious power of inflating itself. 



CARTILAGINOUS FISHES (CHONDROPTERYGIl). 



We may subdivide the cartilaginous fishes into sela- 

 choids, including the sharks, sea-fish, rays, and torpedos, 

 and ganoids, composed of the sturgeon family. The 

 selachoids have no air-bladder ; the ganoids have an air- 

 bladder provided with a duct. 



Selachoids. Sharks are found in all seas, and grow to 

 an enormous size ; some as long as thirty feet having 



FIG. 279. 



WHITE SHARK (Carchariasvulgaris). 



been taken, and these are small compared to extinct 

 species, which measured seventy-five feet or more in 

 length. The mouth of a large shark is sometimes two 

 yards in circumference, and its borders are covered with 

 four or six rows of teeth as sharp and cutting as the 

 teeth of a saw. The voracity of the shark is proverbial ; 

 they swallow everything they come across floating in 

 the water. Ships are often followed by schools of them. 



