STURGEONS AND AM [A 



163 



sensory appendages of fishes. They have been but little 

 studied, and their relations to Acipenser have never been 

 satisfactorily determined. They have certainly many feat- 



Fig. 166 B. The spoon-bill sturgeon or paddle-fish, Polyodon spatula (Walb.), 

 J. and G. X ?. Ventral and side view. Mississippi basin. (After GOODE.) 



ures in skeletal parts, fin structures, lateral line organs, 

 jaws, teeth, which can only be looked upon as of primitive 

 character ; on the other hand, their highly specialized ros- 

 trum, degenerate opercula, and want of dermal amouring 

 would suggest an early divergence from the main stem of 

 the sturgeons. To the writer, Psephurus seems the more 

 generalized of these peculiar forms. 



Fig. 167. The bowfin, Amia calva, L. X \. (After GOODE in U. S. F. C.) 

 Central and Eastern United States. 



Amia calva (Fig. 167) is the last of the recent Ganoids 

 to be noted. Its distribution corresponds closely with 

 that of the gar-pike ; it is a common form, worthless as 



