CHAPTEE XXV. 

 THE MAILED FISHES. 



Abotjt the time that sharks appeared, and perhaps 

 sooner, a very singular group of fishes were ushered into ex- 

 istence, whose vertebral column and skull were gristly, so 

 that their fossil remains consist only of scales, plates, and 

 teeth. These were the forerunners of the modern square- 

 scaled fishes or Ganoids, of which our sturgeon and garpike 

 are examples. 



The term ganoid was applied to these fishes from the 

 form of the scales, which in most of the species are angular, 

 square, or rhomboidal, and covered with enamel, as seen in 

 the common garpike. In others, however, as in the Amia 



Fid. 157.— Spoon-bill Fish. 



and Dipnoans, the scales are rounded or cycloid. The 

 sturgeons (Fig. 156) have the snout long and pointed, with 

 the mouth situated far under the head, and toothless; while 

 the body is protected by a few very large scales. Acipen- 

 ser sturio is the common sea-sturgeon of our coast, ascend- 

 ing rivers. It is sometimes eight to ten feet in length. 



The singular spoon-bill {P'olyodon folium. Pig. 157) is 

 five feet long; it is smooth-skinned, and has a snout one 

 third as long as the body, and spatulate, with thin edges. 

 It has a very wide mouth with minute teeth, and lives ou 



