74 FISHES OF ILLINOIS 



Genus CARPIODES Rafinesque 



(carp-suckers) 



Body more or less thin and compressed, becoming deeper and more 

 arched above with age; ventral line almost straight or but slightly 

 curved downward; head small, short, somewhat compressed; lips thin 

 and slightly striate; bones of skull with generally smoother surfaces 

 and not so heaA-y as in Ictiohiis; a well-developed anterior fontanelle at 

 intercalation of frontals and ethmoid; a supraorbital bone present; pos- 

 terior fontanelle narrowest behind, its posterior margin formed by the 

 converging parietals; suboperculum very broad, subtriangular, its 

 greatest breadth below middle; cheek deep and long, the lower posterior 

 border of the preopercle somewhat angled, the center of orbit equi- 

 distant between its infraposterior angle and the upper corner of the 

 gill-cleft; pharyngeal bones broad but very thin, the teeth very much 

 compressed, weaker than in Ictiobtts; vertebrae 35 or 36; air-bladder 

 in two parts; dorsal fin long, rays 23 to 30, the anterior rays some- 

 times produced into a long filament that may reach almost to the caudal; 

 scales large; lateral line complete; color light, usually more or less 

 silvery ; snout tuberculate in spring males of some species {difjormis 

 and velijer) . 



Four species of these fishes are known in Illinois, mostly of small 

 size, seldom over 12 inches long, and of little or no commercial value. 

 The name of carp was applied to them by the early settlers of Vir- 

 ginia, although they bear only a general resemblance to the Euro- 

 pean species of that name. Since the latter was introduced into our 

 w^aters the native species have been called "American carp." 

 Since they belong to a different family from the foreign species, to 

 which the name was originally given, the common name of carp- 

 sucker, already considerably used, is much to be preferred. 



In Illinois they are distributed throughout the greater rivers of 

 the state and their larger tributaries, and occur also in Lake Michi- 

 gan and the smaller lakes of northern Illinois. They are extremely 

 common in the lakes and ponds of the river bottoms. 



The carp-suckers are rather filthy feeders, swallowing a greater 

 quantity of mud than the nearly related buffalo-fish. The struc- 

 tures of food prehension carry to its extreme a development of the 

 gill-rakers and a correlative degradation of the pharyngeal jaws and 

 teeth. The pharyngeal bones are very thin and brittle, each with 

 about 200 teeth, m.inute above and gradually enlarging downwards, 

 but not thickening or lengthening greatly on the lower part of the 

 arch. The intestine is very slender, and about four times as long as 

 the head and body taken together. The gills are remarkably com- 

 pacted, the upper and lower ends nearly meeting when the mouth 



