ICTIOBUS 73 



Distributed throughout the Mississippi Valley much as the 

 other buffalo are, but tending more generally to deep water, accord- 

 ing to the reports of fishermen. 



It is common in the Mississippi and the Illinois rivers, and in the 

 principal streams of the state at large. It is not so frequently taken 

 in shallow water as the other species, and it is said to have a stronger 

 preference for flowing streams. Nevertheless, it must be said that 

 more than two thirds of the specimens in our collections came from 

 lakes and sloughs, the greater part of the remainder being from 

 rivers of the larger size. 



This buffalo does not average as large as the preceding species, 

 its maximum weight in the Mississippi being, according to Mr. Ash- 

 lock, of Alton, less than 40 lb. 



About a fifth of the food of the specimens examined, consisted of 

 vegetation, mainly duckweed, but with an occasional admixture of 

 terrestrial rubbish. The animal food was divided, with approxi- 

 mate equality, between mollusks, insects, and Entomostraca, the 

 latter taken chiefly in spring when they are present in the greatest 

 abundance. The food of the young of this buffalo consists largely 

 of the minuter forms of the plankton, including especially Protozoa, 

 rotifers, and unicellular alga?. 



The gill-rakers of this species are less numerous than those of 

 cyprinella and scarcely so long, and seem to form a less efficient 

 straining apparatus. The pharyngeal jaws are heavier, triangular 

 in section, and about as thick as high. Seventeen specimens of 

 this species, collected from the Illinois and the Mississippi in vari- 

 ous months from April to October, contained aquatic vegetation 

 amounting to about a third of the total food, the principal element 

 being a small duckweed (Wolffia) especially; abundant where a part 

 of the fishes were taken, and amounting in some cases to 95 per 

 cent, of the contents of the stomach. A larger duckweed, frag- 

 ments of hornwort (Ceratophyllum), diatoms, and other unicellular 

 alga? had also been eaten. Animal food (80 per cent.) was fairly 

 equally divided between mollusks, insects, iand Crustacea, the first 

 (30 per cent.) being mainly a thin-shelled bivalve (Sphcerium) com- 

 mon in the mud. Several specimens had eaten nothing but this 

 mollusk. Chironomus larva? and Entomostraca were the principal 

 other elements, each making practically a fifth of the entire food. 



