454 Illinois State Laboratory of Natural History. 



ened or elongate, about thirty on the lower fourth of the arch. 

 Crowns emarginate or doubly emarginate, with the inner angle 

 similarly produced, forming a hook or cusp. Intestine very 

 slender, four times as long as head and body in the specimen 

 examined. 



Nineteen examples of the species, representing thirteen 

 dates and localities, from April to October, and from 1877 to 

 1887, collected from Crystal Lake in northern Illinois, from 

 the lakes of the Ohio near Cairo, and from the Illinois River at 

 Ottawa, Peoria, and Havana, show that the native carp differs 

 from the other species of Ictiobus chiefly in the inferior amount 

 of vegetation eaten, in the greater quantity of mud mingled 

 with the food, in the absence of the larger insect larvae, and in 

 the lack of univalve Mollusca. It resembles closely Ictiobm 

 cyprinellus, but from this differs also with respect to the vegeta- 

 tion taken, and in its filthy feeding habits. The vegetable food 

 was only eight per cent., mostly Wolffia, and that eaten by 

 only two of the specimens. A few diatoms were mingled with 

 the mud in three, and miscellaneous aquatic vegetation occurred 

 in five. Mollusks made about a fourth of the food, all the 

 thin-shelled Sphaeriuin. Insects averaged about one third, the 

 greater part Chironomus larvae. Neuroptera were eaten by 

 only four of the specimens, and contributed only two per cent, 

 to the food, case-worms (Phryganeidae) being the only forms 

 identified. Entomostraca made nearly a fourth, distributed 

 through a considerable list, which included Simocephalus 

 americanus, Bosmina, Chydorus, Alona, Cypris, Cyclops, and 

 Canthocamptus. No Vermes or Polyzoa were observed, but 

 occasional Protozoa were noticed, especially Centropyxis and 

 Difflugia. 



Looking now at the food of the family, as exhibited by the 

 one hundred and seven specimens discussed, representing, as 

 they do, five genera and eleven species, we conclude that the 

 sucker family is essentially carnivorous, the vegetable food 

 amounting to only eight per cent, of the whole, and no ele- 

 ment of this being especially prominent. The smaller mol- 

 lusks are the most important single class, the ratio of these 

 being forty-one per cent., about three fourths of them Sphae- 

 rium. The large quantity of aquatic insects (one third of 



