418 



Series Plectognathi 



immaculatus, the common species of Japan, is without spines; 

 Ostracion sebce of Hawaii and Samoa is deep, rich blue with 

 spots of golden. Aracana is also of East Indian origin; Ara- 

 cana aculeata, with numerous species, is common in Japan. 



FIG. 354. Hornless Trunkfish, Lactophrys trigonus (Linnaeus). Tortugas, Fla. 



A fossil species of Ostracion (O. micrurum) is known from the 

 Eocene of Monte Bolca. 



The Gymnodontes. The group of Gymnodontes, having the 

 teeth united in a turtle-like beak, carry still further the degen- 



FIG. 355. Skeleton of the Cowfish, Lactophrys tricornis (Linnaeus). 



eration of scales and fins. There is no trace of spinous dorsal, 

 or ventral. The scales are reduced to thorns or prickles, or 

 are lost altogether. All the species have the habit of inflating 

 themselves with air when disturbed, thus floating, belly up- 

 ward, on the surface of the water. Very few, and these only 

 northern species, are used as food, the flesh of the tropical 

 forms being generally poisonous, and that often in a higher 

 degree than any other fishes whatever. 



The Triodontidae. The most generalized family is that of 

 the Triodontida. These fishes approach the Balistidce in several 



