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- 

 bodied 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- 

 vokingly 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 2 5 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 papillae Cycleptus. 



bb. Posterior fontanelle well developed, extending forward between frontals a 

 distance equal to more than J of their length; head 3h to 5 ti:nes in body; 

 lips plicate, striate, or smooth 



c. No 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 f of that to upper comer of gill-cleft ; 

 subopercle broadest at its middle, subsemicircular Ictiobus. 



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

 notching ethnioid; 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, w4th 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 complete and continuous. 



f. Scales small and crowded anteriorly, the number in the lateral line 55 to 110 



(except in C. mgricanns, for which see below ff ) Catostomus. 



ff. Scales large and nearly equal all over the body, 40 to 55 in the lateral line. 



g. Air-bladder in two parts; scales 48 to 55 in lateral line 



Catostomus (Hypentelium) nigricans, 

 gg. Air-bladder in three parts; scales larger, 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 Moxostoina. 



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

 somewhat oblique, lips very thick Placopharynx. 



hh Upper lip not protractile; lower lip in two separate lobes Lagochila. 



