FISHES OF ILLINOIS 



Fig. 4 



Heterocercal tail of Sturgeon {Aci- 



penser) . 



Fig. 5 



Heterocercal tail of Garpike (Lepi- 

 sosteus) . 



Fig. 6 

 Heterocercal tail of Dogfish {Amia). 



Fig. 7 



Typical homocercal tail of Pike-perch 

 (Stizostedion) . (After Jordan and 

 Evermann.) 



Fig. 8 

 Ventral view of head of Large- 

 mouthed Black Bass, showing free 

 gill-membrane. 



Fig. 9 



Ventral view of head of Common 

 Sucker {Cafostomtis commersonii), 

 showing connection of gill-mem- 

 branes. 



