172 FISHES OF ILLINOIS 



Order NEMATOGNATHI 



THE CATFISHES 



Skeleton bony; four anterior vertebrae coossified, modified, and fur- 

 nished with a chain of small bones (Weberian ossicles) connecting the air- 

 bladder (if present) with the auditory organ; ventral fins abdominal; dorsal 

 and pectorals each with a single spine; pectoral arch suspended from the 

 skull; a mesocoracoid arch present; suboperculum wanting, or modified into 

 the uppermost branchiostegal ; premaxillary forming border of mouth (except 

 in the genus Diplomystes, of Chili), the maxillary being often rudimentary 

 and supporting the base of a barbel; air-bladder, if present, with open duct 

 (physostomous). A large group, comprising some 1,200 species and 150 

 genera, found in the fresh waters of both hemispheres and of all the continents, 

 few species being marine; most abundant in the Amazon region. Most 

 species are naked-skinned, although the numerous small forms of the South 

 American family Loricariidce* have the sides and back armored with rough 

 bony plates. 



Family SILURID^E 



THE CATFISHES 



Body more or less elongate, naked or covered (in many South American 

 forms) with bony plates; no true scales; lateral line usually present; skeleton 

 osseous; 4 anterior vertebrae modified, and furnished (in forms in which air- 

 bladder is developed) with a chain of small bones (Weberian ossicles) con- 

 necting the air-bladder with the ear; ventral fins abdominal; anterior rays 

 of dorsal and pectorals usually spinous; an adipose fin usually present; tail 

 not heterocercal ; mesocoracoid present; gill-openings generally wide; sub- 

 operculum wanting, or modified into the uppermost branchiostegal; margin 

 of upper jaw formed by premaxillaries only; teeth in jaws in broad bands; 

 lower pharyngeals separate; air-bladder usually present, simple, with open 

 duct, connected (see above) with the organ of hearing by Weberian ossicles. 



This family is very large and widely distributed, embracing 

 about 700 species, found chiefly in fresh water, in all parts of the 

 globe. Catfishes are most abundant in tropical and subtropical 

 regions. Some species grow to a very large size, and all except 

 the very small forms are of more or less value as food. The 

 giant "sheatfish," or "wels," of Europe, which is abundant in 

 the Danube, reaches a weight of 300 to 400 lb, being next after 

 the sturgeons the largest European fish. There are in the United 

 States, Canada, and Mexico upwards of 35 species of catfishes, 



* Some tropical Silurida: are imperfectly mailed. 



