41 2 



Series Plectognathi 



more or less distinctly scaly. The teeth are separate and 

 incisor-like and the form is compressed. In the Ostracodermi 

 (oarpaxos, a box ; deppa, skin) there is no spinous dorsal, the teeth 

 are slender, and the body is inclosed in an immovable, bony 

 box. In the Gymnodontes (yvj*vo?, naked; odovs, tooth) the 

 teeth are fused into a beak like that of a turtle, either con- 

 tinuous or divided by a median suture in each jaw, the spinous 

 dorsal is lost, arid the body is covered with thorns or prickles 

 or else is naked. 



The Scleroderms. The Sclerodermi include three recent and 

 one extinct families. Of the recent forms, Triacanthidcs is 

 the most primitive, having the ventral fins each represented 

 by a stout spine and the skin covered with small, rough scales. 

 The dorsal has from four to six stiff spines. 



Triacanthodes anomalus is found in Japan, Hollardia hol- 

 lar di in Cuba. Triacanthus brevirostris, with the first spine very 

 large, is the common hornfish of the East Indies ranging north- 

 ward to Japan. 



The Trigger-fishes: Balistidae. The Balistida, or trigger-fishes, 

 have the body covered with large rough scales regularly arranged. 



FIG. 345. The Trigger-fish, Balistes carolinensis Gmelin. New York. 



The first dorsal fin is composed of a short stout rough spine, 

 with a smaller one behind it and usually a third so placed that 

 by touching it the first spine may be set or released. This 



