CYPRIXID.-E — THE MIXXOWS AXD THE CARP 103 



Key to the Genera of Native CYPRINID^E found in Illinois 



(Not including the European carp, Cyprinus carpio Linnaeus, which, with the 

 goldfish, Carassiiis aiiratns Linnaeus, is sufficiently distinguished from all native 

 American Cyprinidcc by the presence of a serrated spine in dorsal and anal fins.) 



a. Intestine more than twice length of body; peritoneum usually black, brown, 



or very dark gray; species generally mud-eaters. 



b. Intestine spirally wound around air-bladder; teeth 4-4 or 1, 4-4, 



Campostoma. 



bb. Intestine not wound around air-bladder. 



c. Scales very small, 65 to 90 in longitudinal series; teeth 5-5, or 4-5 



' Chrosomus. 



cc. Scales larger, about 3 5 to 50 in lateral line; teeth 4-4. 



d. Scales before dorsal 12 to 16 in number, not crowded; first (rudimentary) 



ray of dorsal fin slender, bony, and closely attached to second 



Hybognathus. 



dd. Scales before dorsal small and considerably crowded, 22 to 2 5 in number; 

 first (rudimentary) dorsal ray more or less club-shaped, inclosed in thick 

 skin, and separated from second ray by a distinct membrane . . Pimephales. 



aa. Intestine less than twice the length of body; peritoneum usually pale; 

 species generally carnivorous, or partly so. 



e. Maxillary without barbel*. 



f. Mouth extremelv small and upturned, the angle with vertical formed by its 



cleft less than 40°. 



g. Peritoneum pale; teeth 4-5 or 5-5 Opsopoeodus. 



gg. Peritoneum black: teeth 4-4. Notropis (anogenus only; for main division 



of genus see k, below). 

 ff. Mouth horizontal or more or less oblique, the angle with vertical formed by 

 its cleft usually much more than 40°. 



h. Abdomen behind ventral fins with a sharp keel-like edge over which the 

 scales do not pass; body much compressed; anal fin long, its rays 12 to 



14; teeth 5-5 Abramis. 



hh. Abdomen behind ventrals never sharply keeled, but rounded and fully 

 scaled; form various, elongate or fusiform, or more or less compressed. 



i. First (rudimentary) ray of dorsal club-like, covered with thick skin, and 

 separated from second ray by a distinct membrane; teeth 4-4. . .Cliola. 



ii. First (rudimentary) ray of dorsal slender and bony and closely attached to 



second. 

 j. Lips normal, nowhere conspicuously thickened; the mouth subterminal, 



more or less oblique. 



k. Lower portion of head rounded, not swollen, and without externally visible 

 mucus channels; teeth in the main row normally 4-4, the lesser row often 

 wanting Notropis. 



each main (outer) row, and 2 in each lesser (inner) row; "teeth 4-4" means that 

 there is but a single row on each pharyngeal bone; while "1, 4-4, 0" would indi- 

 cate that the lesser row is represented on one side but not on the other. The 

 teeth may be removed for study in the smaller species by the use of a needle or 

 small hook, or fine forceps, which should be inserted through the gill-opening at 

 the back of the opercular cavity and directly under the shoulder girdle. A con- 

 venient mode of removal consists in grasping the shoulder of the pharyngeal arch 

 with the forceps and pulling forwards, after first taking care to cut loose the 

 attachments of the upper and lower limbs. The whole operation may be per- 

 formed without removing the opercle, which may be merely lifted up to allow 

 room for insertion of the forceps. 



* Care should be exercised here, as a barbel may be present but concealed. 



