24 ILLINOIS BIOLOGICAL MONOGRAPHS [194 



Ophidon. The dorsal edge of the bone is drawn out into a long slender 

 process which lies on the posterior edge of the shank of the hyomandi- 

 bular. 



The mandible is shorter than in Ophidon. There is no ridge on the 

 lateral surface of the dentary nor is there a cavity within it ; also there 

 is no mesial process on the ventral edge. It possesses villi form teeth 

 but there seems to be a modification of the teeth in the inner row. These 

 are longer than the others and have assumed more or less of a canine 

 shape, placing the Scorpionichthys and Ophidon closer together. 



