PISHES OF ILLINOIS 



Fig. 4 

 Heterocercal tail of Sturgeon (Aci- 



penser) . 



Fig. 5 

 Heterocercal tail of Garpike (JLepi- 

 sosteus) . 



Fig. 6 

 Heterocercal tail of Dogfish (Amia). 



Fig. 7 

 Typical homocercal tail of Pike-perch 

 (Stizostediori) . (After Jordan and 

 .Evermann.) 



Fig. 8 

 Ventral view of head of Large- 

 mouthed Black Bass, showingfree 

 gill-membrane. 



Fig. 9 

 Ventral view of head of Common 

 Sucker (Catostomus commersonii), 

 showing connection of gill-mem- 

 branes. 



