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 heavy as 

 in Ictiobus; a well-developed anterior fontanelle at intercalation of f rentals 

 and ethmoid; a supraorbital bone present; posterior 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 equidistant 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 Ictiobus; 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 (difformis and velifer). 



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

 small size, seldom over 12 inches long, and of little or no com- 

 mercial value. The name of carp was applied to them by the 

 early settlers of Virginia, although they bear only a general 

 resemblance to the European species of that name. Since the 

 latter was introduced into our waters 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 

 Michigan 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 structures of food prehension carry to its extreme a develop- 

 ment 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, minute above and 

 gradually enlarging downwards, but not thickening or lengthen- 

 ing 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 compacted, the upper 



