66 FISHES OF ILLINOIS 



almost directly downward, each furnished with 5 or 6 rows of strongly de- 

 veloped tubercle-like papillae; lower lip incised behind; eye very small, located 

 a little back of center of head, 6 to 8.3 in its length; interorbital space convex, 

 about 2 in head. Dorsal rays 31 to 32, the first two developed rays elevated 

 to about Yi the length of base of fin, the succeeding rays rapidly shortened 

 to about the eighth, the remaining rays all low and of about equal height; 

 position of dorsal well forward, the distance from insertion of fin to muzzle 

 2.2 to 2.4 in length of body; caudal deeply forked, the lobes about equal. 

 Scales 9 or 10, 55-58, 8-10, much longer than broad, much crowded on nape, 

 breast, and belly, and at base of dorsal fin; lateral line complete. 



This peculiar species, the only one of its genus, is confined 

 to the Ohio and the Mississippi rivers. It is reported abundant 

 at Pittsburgh, but is not common in the Mississippi above the 

 latitude of Quincy. It is frequently taken in spring at Cairo 

 and at Grafton, on the Mississippi, and in the lower part of 

 Rock River, but it disappears from the product of the fisheries, 

 except for an occasional specimen, about the last of June, as 

 soon as the spring run is over. It is also caught in spring in 

 considerable quantities in the Illinois River, but much less 

 abundantly now than in former years. To Illinois and Missis- 

 sippi River fishermen in this state it is commonly known as the 

 Missouri sucker, or occasionally as the black sucker. The 

 name "black-horse" we have not found in current use. 



It reaches a length of 2 or 2^ feet, and Ashlock reports 

 specimens taken at Alton of a weight of 16 pounds. As a food 

 fish it is the best of the suckers. It is caught on set-lines as well 

 as in fyke-nets and with seines. Its habits are but little known, 

 but it apparently lives in the deeper water of the river channels, 

 except during the spawning migration. Eggs are deposited 

 in May and June. 



Genus ICTIOBUS Eafinesque 



Body robust, compressed, both dorsal and ventral outlines curved; head 

 rather large; mouth terminal or slightly inferior; lips thin, plain or more or 

 less strongly plicate, the upper protractile, the lower lobed at corners of 

 mouth, plicate. The generally heavier bones, with more or less roughened 

 surfaces, and the different configuration of certain cranial elements (see key 

 to genera of Catostomidce) in Ictiobus furnish the most reliable means of dis- 

 tinction between this genus and Carpiodes. Frontals joined closely with 

 ethmoid, obliterating anterior fontanelle, posterior fontanelle large, some- 

 what narrowed forward, its 'posterior margin formed by the supraoccipital; 

 a supraorbital bone present; suboperculum symmetrically rounded, sub- 

 semicircular, broadest at its middle; cheek shorter and not so deep as in 

 Carpiodes, the lower posterior border of the preopercle a gentle curve, the 



