The Food of Fresh-Water Fishes. 451 



ICTIOBUS CYPEIXELLUS, C. & V. ReD-MOUTH BuFFALO. 



The statements made coueerning the abundance, distri- 

 bution, and commercial value of the preceding species will ap- 

 ply equally well to this. The fishermen report, however, 

 that the quill-back frequents deeper water than the red-mouth. 

 The structures of food prehension differ from those of bubalus 

 in the lighter pharyngeal jaws, the greater number and smaller 

 size of the teeth, and the more efficient branchial apparatus. 

 The pharyngeal jaws are relatively thin, the thickness being 

 about one fourth the height. The teeth are about seventy-five 

 in number on each jaw, minute above, gradually but not greatly 

 thickened below, the ten lowest occupying nearly one fifth the 

 length of the jaw. These largest teeth have the cutting edges 

 obtuse, and are slightly hooked within. The remaining teeth 

 are more or less crenate on the cutting edge, each with con- 

 spicuous hook or cusp at the inner angle. The posterior edges 

 are also acute. 



The gill-rakers are similar to those of the quill-back, but 

 more efficient as a straining apparatus. The longer rakers of 

 the anterior row (seventy-five in number) are fully equal in 

 length to the corresponding filaments, and are armed within 

 with a double row of clusters of minute teeth. Eight or ten of 

 the lower rakers are fused in the form of thick oblique ridges, 

 The tips of the rakers of the other rows project beyond the 

 borders of the arches a distance about equal to the line of at- 

 tachment to the arch. The pharyngeal enlargements are very 

 conspicuous and thick, nearly filling the pharyngeal cavity. 



in length from seven eighths of an inch to two inches, fed largely 

 upon unicellular Algje and rotifers, the remainder of their food being 

 chiefly the smallest Entomostraca. I add here the details from two 

 additional specimens, taken in June, from the Illinois River, at 

 Pekin, one three fourths of an inch in length and the other eight 

 tenths. The greater part of the food of these consisted of rotifers. 

 Protozoa, and gelatinous and other unicellular Algje, a single Bos- 

 mina in each being the only entomostracan form determined. The 

 rotifers included Brachionus and Anurea ; and among the Protozoa 

 were Actinosphcerium, Arcella vulgaris, and .4. discoidea. Closterium 

 was noticed among the Algse, with numerous gelatinous Algse related 

 to Protococcus, and a filament of OsciUatoria. Spores of fungi were 

 found in both, and a fragment of vegetation penetrated by a fungus 

 mvcelium occurred in one. 



