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 Familip:s of EVENTOGNATHI rorixD ix Illinois 



a. Dorsal flns of more than 25 rays, or shorter and the lips thickened and covered 

 with plicate or papillose slvin; pharyngeal teeth numerous and comb-like 



Catostomidae. 



aa. Dorsal fln 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/E 



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 vertebrse modified and provided 

 with Weberian apparatus or ossicula auditus; fins wdthout 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; pseudobranchise 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 singe row of numerous comb-like teeth; mouth usually p:'0- 

 tractile and with fleshy hps (sucker-hke) ; ahmentary canal long; stomach 

 simple: no pyloric caeca; air-bladder large. di\aded 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 

 IlHnois, 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 generalh^ distributed 

 of our larger fishes. 



