2854 



THE BONY FISHES AND GANOIDS 



Externally, the moon eye (Hyodon tergisus), as the single repre- 

 sentative of the first of the two families is popularly termed, has the 

 body covered with cycloid scales, the head naked, and no barbels. The margin of 

 the upper jaw is formed by the premaxillae in front and the maxillae at the sides, 

 the latter bones being articulated to the former at the point of junction; and all the 

 elements of the gill cover are present. There is no fatty fin, and the short dorsal 

 is placed in the caudal region, above the fore part of the longer anal; the caudal fin 

 being forked. The gill openings are wide; the stomach is horseshoe shaped, the 



CHISEL JAW AND MOON EYE. 



(One-third natural size.) 



intestine short, and the air bladder simple; false gills being absent. In form 

 the body is oblong and compressed, with a part of the lower surface forming 

 a sharp edge; and the cleft of the mouth is somewhat oblique; all the bones of 

 the palate bearing small teeth, and the edges of the tongue carrying a larger 

 series. Before their exclusion, the eggs fall into the cavity of the abdomen. 

 The moon eye, shown in the lower figure of the above illustration, grows to a 

 length of from one foot to eighteen inches, and is confined to the fresh waters 

 of North America, where it is abundant in the lakes and rivers of the western side 

 of the continent. 



