Tlie Food of Yo'ioxj Fishes. 79 



the remainder of the food consisted of Copepoda and C^la- 

 docera. These specimens were taken from the Illinois K. 

 in early June. 



Four (Xii'p- suckers (Carpiodes), seven-eighths inch to two 

 inches long, taken from the Illinois and from Clear L., in 

 Kentucky, had fed like the preceding genus, except that 

 the Entomostraca were in larger quantity (forty-eight per 

 cent.), and included a number of Ostracoda, while the ro- 

 tifers were comparatively few. The Daphniida? of the 

 Illinois R. specimens were nearly all Scapholeherls mucro- 

 nata. Oanthocamptus in trivial numbers was also found 

 in a single specimen. 



Reviewing the food of these thirty young suckers, we 

 see that they differ from the other families studied in the 

 larger food-resources open to them ; for, while the struc- 

 ture of their mouths does not prohibit their taking Ento- 

 mostraca, it enables them to draw upon the multitudes of 

 minute organisms found upon the bottom. Evidently they 

 have no means of selecting such microscopic structures 

 from the mud in which these most frequently rest, and 

 considerable quantities of dirt are consequently often 

 found in the intestines; but from the "richness" of the 

 contents I infer that they doubtless have the power of dis- 

 tinguishing mud containing a large percentage of organic 

 matter from relatively barren portions. 



SiLURID.T.. 



Numerous specimens of the young of this family show 

 that, notwithstanding its many peculiarities of structure 

 and habit, it is no exception to the general rule respecting 

 the food of the young. The smallest of these specimens 

 were from a little school of minute fry, taken in June 

 from the friendly protection of an old oyster-can in the 

 Illinois R. These little creatures were colorless and seem- 

 ingly almost helpless, and only three-eighths of an inch in 

 length. They had already begun to eat, however, and 

 their stomachs were well filled with Cyclops and a few 

 Daphnids and Ohironomus larvae. These were certainly 

 Amiurus, but it was of course impossible to tell the spe- 

 cies. 



