66 FISHES OF ILLINOIS 



considerably beyond the decidedly inferior mouth; distance from eye 

 to muzzle 2 to 2.2 in head; mouth small, its width from 5.8 to 6 in head; 

 lips rather thick, protractile almost directly downward, each furnished 

 with 5 or 6 rows of strongly developed 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 ^ 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 onl}^ one of its genus, is confined to 

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

 Pittsburg, but is not common in the Mississippi above the latitude 

 of Quincy. It is frequent!}^ taken in spring at Cairo and at Grafton, 

 on the Mississippi, and in the lower part of Rock River, but it dis- 

 appears 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 

 Rix'er, but much less abundantly now than in former years. To- 

 Illinois and Mississippi 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 Rafinesque 



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 comers of mouth, plicate. The generally heavier bones, with 

 more or less roughened surfaces, and the dift'erent configuration of 

 certain cranial elements (see key to genera of Catostomidcs) in Ictiobus 

 furnish the most reliable means of distinction between this genus and 

 Carpiodes. Frontals joined closelv with ethmoid, obliterating anterior 

 fontanelle, posterior fontanelle large, soraewhat narrowed forward, 

 its posterior margin formed by the supraoccipital; a supraorbital 

 bone present; suboperculum symmetrically rounded, subsemicircular. 



