STURGEONS AND AMIA 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.), 
jJ.and G. xX}. 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 }. 
Central and Eastern United States. 
(After GOODE in U. S. F. C.) 
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 
