448 ininois State Lahoratonj of Natural History. 



mined Lynceidre), a much larger proportion of Protozoa 

 (especially Difflugia and Arcella), a few Squamella and other 

 rotifers, and unicellular Algse, including Protococcus, Chroococ- 

 cus, Closterium, and Cosmarium. 



Genus Ictiobus. Buffalo and River Carp. 



In this genus are included only the deeper-bodied suckers 

 with light pharyngeal jaws and relatively long gill-rakers. The 

 species differ, however, in these particulars, and may be arranged 

 in a series exhibiting a progressive lengthening of the gill 

 structures, a lightening of the pharyngeal jaws, and an increase 

 in number and a decrease in size of the pharyngeal teeth. 

 Related to these differences of structure are the inferior impor- 

 tance of mollusks in the food (especially of the thick-shelled 

 univalves), the greater number of insects, the appearance of 

 Entomostraca as an important element, and the considerable 

 percentage of vegetation taken. The insects eaten are well dis- 

 tributed instead of being essentially limited, as in Moxostoma, 

 to dipterous larva3. In short, correlatively with the greater 

 number and smaller size of the pharyngeal teeth, the weaker 

 jaws, and the greater development of the straining apparatus, 

 in Ictiobus we find the food generalized, and drawn from 

 numerous sources; while in Moxostoma the food and the food 

 prehensile structures are specialized in the direction of a rather 

 close dependence on the smaller mollusks. 



The feeding habits of these fishes, like those of all species 

 inhabiting the muddy waters of central Illinois, are very difticult 

 of determination, but several fishermen, and others with unusual 

 opportunities for observation, have reported to me that one or 

 more species of this genus have the peculiar habit of whirling 

 around in shallow water or plowing steadily along, with their 

 heads buried in the mud, and their tails occasionally showing 

 above the surface. These operations have nothing to do with 

 spawning, and it is likely that fishes thus engaged are burrow- 

 ing for small mollusks and for mud-inhabiting larvae. 



Ictiobus bubalus, Raf . Quill-back ; Small-mouthed Buffalo. 



This is a very abundant fish in the larger streams and in 

 the lakes and river bottoms, being one of the three species most 



