64 FISHES OF ILLINOIS 



longer and more numerous, making a more effective straining 

 apparatus, and the intestines become longer and smaller. Cor- 

 responding to these differences of structure, mollusks form a larger 

 percentage of the food of the cylindrical suckers, and Entomostraca 

 and vegetable food a very much greater part of that of the deep- 

 b( idied species. All the species commonly swallow much mud, since 

 they collect most of their food from the bottom by suction, to which 

 their protractile mouths and fleshy lips are peculiarly adapted. 



As food fishes they do not hold a high place, the flesh being 

 rather coarse, dry, and either flavorless or strong, and always pro- 

 vi kingly full of small bones. The buffalo and sucker fishery is 

 nevertheless an important one in the Mississippi Valley and the 

 Great Lake region. (See under Ictiobus.) Of the 15 species found 

 in the waters of the Illinois alone, about one third have a greater or 

 less commercial value. 



Key to the Genera of CATOSTOMIDjE found in Illinois 



a. Dorsal fin elongate, with 25 to 40 developed rays. 



b. Posterior fontanelle almost obliterated by the union of the parietals; head 



small and slender, its length 6 to 7 times in body; lips with several series 



of tubercle-like papiike Cycleptus. 



bb. Posterior fontanelle well developed, extending forward between f rentals a 

 distance equal to more than i of their length; head 3J to 5 times in body; 

 lips plicate, striate, or smooth 



c. X" anterior fontanelle, the frontals being closely joined with the ethmoid; 



cheek somewhat shallow and foreshortened, distance from eye to lower 

 posterior angle of preopercle about § of that to upper corner of gill-cleft; 

 subopercle broadest at its middle, subsemicircular Ictiobus. 



cc. Anterior fontanelle well developed, separating anterior edges of frontals and 

 notching ethmoid; cheek relatively deep and long, eye about equidistant 

 between upper corner of gill-cleft and infra-posterior angle of preopercle; 

 subopercle broadest below its middle, subtriangular Carpiodes. 



aa. Dorsal fin short, with 10 to 18 developed rays. 



d. Lateral line more or less incomplete or wholly wanting; scales large and uni- 



formly distributed, .30 to 50 in lateral line 



e. Lateral line entirely wanting at all ages Erimyzon. 



ee. Lateral line more or less developed in adults Minytrema. 



dd. Lateral line plete and continuous. 



f. Scales small and crowded anteriorly, the number in tin- lateral line 55 to 1 1 o 



p1 in ( ', mgricanus, for which see below ff) Catostomus. 



ff. Scales large and nearly equal all over the body, 4(> to 55 in the lateral line. 



g. Air-bladder in two part , cales 48 to 55 in lateral line 



Catostomus (Hypentelium) nigricans, 

 gg. Air bladder in three parts; si all il irger, 40 to 50 in lateral line 

 h. Upper lip protractile, lower entire or incised only part way to anterior mar- 

 gin. 



i. Pharyngeal teeth compressed; mouth wholly inferior Moxostoma. 



ii. Lower pharynge il teeth much enlarged, subcylindrical and truncate; mouth 



s ewhal oblique, lips verj thick Placopharynx. 



hh Upper lip not protrai tile; 1' >\\ er lip in two separate 1 ibes Lagochila. 



