4 



FISHES OF ILLINOIS 



Fig. 4 

 Heterocercal tail of Sturgeon (Acipenser). 



Fig. 5 



Heterocercal tail of Garpike (Lepisos- 

 teus) . 



Fig. 6 



Heterocercal tail of Dogfish (Amia). 



Fig. 7 



Typical homoceical tail of Pike-perch 

 (Stizostedion) . (After Jordan and 

 Evermann.) 



Fig. 8 



Ventral view of head of Large-mouthed 

 1 Black Ba?s, showing free gilt-mem- 

 brane. 



Fig. 9 



Ventral view of head of Common Sucker 

 (Calostomus commersonli), showing con- 

 nection of gill-membranes. 



