FISHES OF ILLINOIS 



FIG. 4 

 Heterocercal tail of Sturgeon (Acipenser) . 



FIG. 5 



Heterocercal tail of Garpike (Lepisos 

 tens). 



FIG. 

 Heterocercal tail of Dogfish (Amia). 



FIG. 7 



Typical homocercal tail of Pike-perch 

 (Stizostedion). (After Jordan and 

 Evermann.) 



FIG. 



Ventral view of head of Large-mouthed 

 Black Bass, showing free gill-mem- 

 brane. 



FIG. 9 



Ventral view of head of Common Sucker 

 (Catostomus commersonli) , showing con- 

 nection of gill-membranes. 



