THE TRUE FISHES. 193 



Porcupine-Fishes (Tetradontida>). These fishes are 

 often covered with sharp spines, and when removed from 

 the water they innate themselves with air, resembling an 

 oval, spiny balloon.* Each jaw is divided in the middle, 

 so that they appear to have four teeth. The diodons are 

 allied forms. 



Sunfishes \ (prthagoriscidtz). These are oval or ob- 

 long in shape (Fig. 236). The dorsal and anal fins are 



FIG. 236. Sunfish (Orthagoriscus mo la). 



* They are often figured in this shape, but it is unnatural, and 

 only attained when the fish rs forcibly taken from the water. The 

 Diodon antennatus has undivided, teeth-like mandibles, so power- 

 ful that when swallowed by a shark they have been known, accord- 

 ing to Darwin, to eat their way out through th? stomach and skin of 

 the fish. 



f They are sluggish fishes, rolling along at the surface, and are 

 quite common on the eastern coast of the United States and in 

 other seas. The body is covered with a thick mucus and infested 

 by parasites, goose-barnacles even living in its mouth. Semper and 

 Cobbold refer to its luminous qualities. They attain a height of six 

 feet, and weigh five or six hundred pounds. The liver alone is 

 valuable. 



