FISHES OF ILLINOIS 



FIG. 4 

 Heterocercal tail of Sturgeon (Acipenser). 



FIG. 5 



Heterocercal tail of Garpike (Lepisos- 

 ieus). 



FIG. 6 

 Heterocercal tail of Dogfish (Amia). 



FIG. 7 



Typical homoceical tail of Pike-perch 

 (Stizostediori) . (After Jordan and 

 Evermann.) 



Ventral view of head of Large-mouthed 

 Black Bass, showing free gill-mem- 

 brane. 



Fro. 9 



Ventral view of head of Common Sucker 

 (Catostomus commersonli) , showing con- 

 nection of gill-membranes. 



