The Food of Fresh-Water Fishes. 441 



of the gill-rakers, correlated with an increase in length of the 

 pharyngeal bones and in the number of their teeth, and a 

 converse diminution in the size and strength of these structures. 

 The intestine also becomes longer and smaller as one passes 

 from the cylindrical suckers to the deep-bodied buffalo and carp. 

 The data concerning the food of this family here presented 

 are drawn from a study of the alimentary contents of one 

 hundred and nine specimens, collected chiefly from the Illinois 

 and Mississippi Rivers and their immediate tributaries. They 

 indicate, in general, that about one tenth of the food consists 

 of vegetation, taken chiefly by the buffalo fishes (Ictiobus),and 

 in them largely composed of distillery slops. Mollusks and 

 insects appear in nearly equal ratio in the food of the family at 

 large, the former taken much the more generallv by the 

 cylindrical suckers, with heavy pharyngeal jaws and solid teeth, 

 and the latter about equally by all, with the single exception of 

 the stone roller ( Hypentelium ), whose peculiar haunts and feed- 

 ing habits explain its departure from the average. On the other 

 hand, the ten per cent, of Entomostraca were eaten chiefly by 

 the deeper-bodied species. 



Placopharynx carinatus. Cope. 



This species has the general appearance of one of the red 

 horse (Moxostoma), and has possibly been commonly over- 

 looked in our collections, as we have noted it very rarely. 



Its branchial apparatus is not noticeably different from 

 that of the following genus, the gill-rakers being short and 

 few, and effective only on the upper part of the arch, the lower 

 arm being, like that of Moxostoma, covered by a ridged pad. 



The fish is very remarkably distinguished, however, by the 

 heavy pharyngeal jaws and the thick and strong pharyngeal 

 teeth with conspicuous grinding surface. The latter number 

 about thirty on each pharyngeal, the upper ones minute and 

 useless rudiments, the lower ten very large, occupying about 

 two thirds the length of the arch, — the lower six, in fact, 

 one half of it. It is altogether likely that this apparatus is 

 related to a preference for molluscan food, but the number of 

 specimens available for my examination was too small to verify 

 this supposition. 



