CARPIODES CARP-SUCKERS /3 



is closed, and the longest of the anterior series are a little longer 

 than the corresponding filaments. 



Nineteen specimens, representing 13 localities from extreme 

 northern to extreme southern Illinois, and various dates from April 

 to October, indicate that our native carp differ from their near 

 allies, the buffalo-fishes, in the smaller amount of vegetation eaten, 

 in the greater quantity of mud mingled with the food, and in a de- 

 ficiency of the larger insect larvse. The vegetable food of these 

 specimens was only 8 per cent., mostly the small duckweed, Wolffia. 

 Mollusks made about a fourth of the food, all the thin-shelled bivalve 

 Sphcsrium. Insects averaged about a third, the greater part larvse 

 of Chironormis. Entomostraca made nearly a fourth, and included 

 a considerable list and ^'ariety of our more abundant species. 



Key to the Species of CARPIODES found in Illinois 



a. Snout short, 3-1 to 4^ in head; nostrils Avell forward, the distance from an- 



terior nostril to end of snout considerably less than diameter of eye; tip of 

 lower jaw little in advance of nostrils. 



b. Body robust, subfusiform, depth 2| to 3 in length; snout obtusely pointed; 



eye moderate, 4i- to 5 in head; anterior rays of dorsal scarcely elevated, 

 osseous at base; large species, reaching over 5 fb in weight carpio. 



bb. Body thin and compressed, the back much elevated in adults, depth 2^ to 

 2 J in length; snout very blunt, sqtiarish at tip; eye large, 3f to 4-i in head; 

 anterior rays of dorsal much lengthened, sometimes equaling length of 

 base of fin; small species, not over 12 inches in length difformis. 



aa. Snout longer, 3 to 3\ in head; nostrils sitiiated well back, the distance froin 

 anterior nostril to end of snout usually greater than diameter of eye; tip 

 of lower jaw far in advance of nostrils. 



c. Body robust, subfusiform, depth 2| to 3h in length; anterior rays of dorsal 



scarcely elevated, about -i length of base of iin; halves of lower tip meeting 

 at a wide angle; large species, reaching a weight of 5 tb thompsoni. 



cc. Body compressed, the back more or less arched, depth 2 -J to 3 in length; 

 anterior rays of dorsal much elevated, nearly or more than equaling 

 length of base of fin; halves of lower lip meeting at a sharp angle; species 

 of small size, not exceeding 12 inches velifer. 



