ORDER EVEXTOGNATHI 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 rays, or shorter and the lips thickened and covered 

 with plicate or papillose skin; pharyng-eal 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 CATOSTOMIDAE 



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 vertebrae modified and provided 

 with ^yeberian 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; pseudobranchiae present; branchiostegals 3; margin 

 of upper jaw formed in the middle by the small premaxillaries, and on the 

 sides by the maxillaries; jaws toothless; lower pharyngeal bones falciform, 

 armed with a sing e row of numerous comb-like teeth; mouth usually pro- 

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

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

 verse constrictions, not surrounded by a bony capsule, communicating with 

 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 prom- 

 inence 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. 



