438 Illinois State Laboratori/ of Natural Historij. 



dorsal portion of each gill projects far forward in the palatal 

 region, and then turns abruptly backward, forming an acute 

 angle in the roof of the mouth. This course of the arches is 

 necessitated by the large accessory organ upon the fourth 

 branchial arch.* The arches are all provided with numer- 

 ous short rakers projecting horizontally upon either side, and 

 forming an unusually effective straining apparatus. The in- 

 testine is very long and slender and much convoluted, the 

 oesophagus small and long, and the stomach very short and 

 muscular, like the gizzard of a granivorous bird. The small 

 intestine is beset with a multitude of slender coeca, and its 

 mucous surface is everywhere remarkably villose. 



The species was represented in our collections by many 

 specimens, but the food was so uniform in character that a 

 prolonged study of it seemed unnecessary, especially as the 

 critical analysis of such large quantities of material, minutely 

 divided and thoroughly intermingled, was a very tedious and 

 time-consuming process. 



The adult specimens examined were eleven in number ; 

 ten from the Illinois river between Havana and Ottawa, and 

 one from the Pecatonica, in northern Illinois. Eight dates and 

 five localities are represented by them, the former ranging from 

 April to October. 



The species has, in general, the habit of swallowing quan- 

 tities of fine mud, containing, on an average, about twenty per 

 cent, of vegetable debris. Occasionally, in the vicinity of dis- 

 tilleries, it feeds, like the buffalo fish, on distillery slops, and 

 sometimes a greater percentage of vegetation occurs mingled 

 with the mud. Traces of animal food were common; but the 

 ratio in most of ray specimens was insignificant, averaging only 

 four per cent, of the whole; although in one shad taken in 

 spring in northern Illinois one fourth of the food consisted of 

 Entomostraca (Cypris). Univalve mollusks occurred in one, 

 fragments of Coleoptera in another, and young Corixa in still 

 another; and spiders and water mites were also noted. Five 

 specimens, in all, had taken Entomostraca — four of them 



* This accessory organ is correlated by Sagemehl with the li- 

 mophagous habit of the fishes in which it occurs.— Morphologisches 

 Jahrbuch, XII., p. 318. 



