16 PEELIMINARY REPORT 



KEY TO THE GENERA OF SILURIDJ:. 



A. Adipose fin conspicuous, its posterior margin free and not contin- 

 uous with the caudal. 

 B. Teeth on the premaxillaries arranged in a slight curve, the 

 ends of the band not extending back on the sides of the 

 mouth. 

 C. Bones of the head continuous with those at the base of 

 the first dorsal (determined by pressing gently on the 

 upper part of the body between the dorsal fin and the 

 head). Caudal fin deeply forked. (Channel Cat) Ictaluriis, 16 

 CC. Bones of the head not continuous with those at the base 

 of the first dorsal (determined as in C). 



(Bull-head) Aiiieiurus, 17 

 BB. Premaxillary band of teeth arranged in horseshoe-shape, the 

 ends extending back on the sides of the mouth; dorsal 



spine little developed (Mudcat) Leptops, 19 



AA. Adipose fin continuous with the caudal. 



B. Band of teeth on the upper jaw with a backward extension 



on each end (Stone Cats) Noturiis, 19 



BB. No backward extension at the ends of the band of teeth on 



the upper jaw (Mad Toms) Schilbeocles, 19 



Genus ICTALURUS Eafinesque. 



Ictalurus punctatllS (Eafinesque). Channel Cat. Silver Cat. White Cat. 



Barbels long, color light olive; lighter on the sides; scarcely 

 ever dark like the bull-heads; generally covered with dark, circu- 

 lar spots; body rather slender; spines large, strong and sharp, the 

 pectoral serrate behind; eye large, located about midway between 

 snout and the end of the opercle. Mouth small; head contained 

 four times in the length; depth 5. This fish reaches a length of 

 three feet and a weight of 20 to 25 pounds. It is reported by Mr. 

 Cram as common in the Minnesota River near Mankato each 

 spring. It is no doubt common in all the large streams in the state. 

 It has been taken in the Red River of the North at Moorhead and 

 at Grand Forks (N. D.) ; in the Otter Tail River at Breckenridge and 

 Red Lake River at Grand Forks (N. J).) and Crookston (Woolman^ 

 1892, Report U. S. Fish Comm., 1893). 



