CAEPIODES CARP-SUCKERS 75 



and lower ends nearly meeting when the mouth 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 deficiency of the larger insect larvae. 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 Sphcerium. Insects averaged about a third, the 

 greater part Iarva3 of Chironomus. Entomostraca made nearly a 

 fourth, and included a considerable list and variety of our 

 more abundant species. 



KEY TO THE SPECIES OF CARPIODES FOUND IN ILLINOIS 



a. Snout short, 3% to 4% in head; nostrils well 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, 4% to 5 in head; anterior rays of dorsal scarcely elevated, 



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



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



2% in length; snout very blunt, squarish at tip; eye large, 3% to 4% 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 situated well back, the distance from 



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 3% in length; anterior rays of dorsal 



scarcely elevated, about % length of base of fin; halves of lower tip meeting 



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



cc. Body compressed, the back more or less arched, depth 2% 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. 



