ORDER EVENTOGNATHI THE CARP'-LIKE FISHES 61 



Order EVENTOGNATHI 



(the carp-like fishes) 



Skeleton osseous; anterior vertebrae modified, with Weberian appa- 

 ratus; fins without spines in typical forms; ventral fins abdominal; 

 pectoral arch suspended from the skull ; a mesocoracoid present ; opercular 

 bones all present; branchiostegals few, usually 3 or 4; air-bladder with 

 open duct; jaws without teeth. Species exceedingly numerous, in all of 

 the streams and lakes of the northern hemisphere. 



Key to Families of EVENTOGNATHI found in Illinois 



a. Dorsal fins of more than 25 raj's, or shorter and the lips thickened and 

 covered with plicate or papillose skin; pharyngeal teeth numerous and 



comb-like Catostomidae. 



aa. Dorsal fin of not more than 10 rays; lips usually thin, never plicate or papil- 

 lose; pharyngeal teeth fewer than 8 on a side, in 1 to 3 rows. . . Cyprinidae. 



Family CATOSTOMID^ 



(the suckers) 



Body oblong or elongate, usually more or less compressed, covered 

 with large or small cycloid scales; head naked; lateral line usually 

 present; belly not serrated; skeleton osseous ; anterior 4 vertebras modi- 

 fied and provided with Weberian apparatus or ossicula auditus; fins 

 without spines; ventrals abdominal; no adipose fin; tail more or less 

 forked; a mesocoracoid arch present; gill-membranes more or less 

 united to the isthmus, restricting the gill-openings to the sides; pseudo- 

 branchias present; branchiostegals 3; margin of upper jaw formed in 

 the middle by the small premaxillaries, and on the sides by the maxil- 

 laries; jaws toothless; lower pharyngeal bones falciform, armed with 

 a single row of numerous comb-like teeth; mouth usually protractile 

 and with fleshy lips (sucker-like) ; alimentary canal long ; stomach 

 simple; no pyloric caeca; air-bladder large, divided into 2 or 3 parts by 

 transverse constrictions, not surrounded by abony capsule, communi- 

 cating with the oesophagus by a slender open duct. 



One of the most striking characteristics of the fish fauna of 

 Illinois, and indeed of the whole Mississippi Valley, is the promi- 

 nence of the sucker family, which includes, within the limits of this 

 state, eight genera and fifteen recognized species, several of them 

 among the most abundant and most generally distributed of our 

 larger fishes. 



