480 Illinois State Laboratori/ of Natural History. 



Only the catfishes seem to have acquired defensive struct- 

 ures equal to their protection, the predatory apparatus of the 

 carnivorous fishes having elsewhere outrun in development the 

 protective equipment of the best-defended species. 



Among the soft-finned fishes the most yaluable as food 

 for other kinds is the gizzard shad (Dorosoma), — this single 

 fish being about twice as common in adults as all the minnow 

 family taken together. It made forty per cent, of the food of 

 the wall-eyed pike; a third that of the black bass; nearly 

 half that of the common pike or "pickerel"; two thirds that 

 of the four specimens of golden shad examined; and a third of 

 the food of the gars. The only other fishes in whose stomachs 

 it was recognized were the yellow cat (Amiiirus natalis) and 

 the young white bass (Roccus). It thus seems to be the especial 

 food of the large game fishes and other particularly predaceous 

 kinds. 



The minnow family ( Cyprinidse) are in our waters especially 

 appropriated to the support of half- grown game fishes, and 

 the smaller carnivorous species. They were found in the wall- 

 eyed pike, the perch, the black bass, the blue-cheeked sunfish, 

 the croppie, the pirate perch, the pike, the little pickerel,' 

 the chub minnow,^ the yellow cat, the mud cat, the dog-fish, 

 and the gar. 



Suckers (Catostomatidte) I determined only from the pike, 

 the sheepshead, the blue-cheeked sunfish, the yellow cat, 

 and the dog-fish (Amia). Buffalo'^ and carp* occurred in the 

 pike, the dog-fish, and the above sunfish. 



MOLL.USK EATERS. 



The ponds and muddy streams of the Mississippi Valley are 

 the native home of mollusks in remarkable variety and num- 

 ber, and these form a feature of the fauna of the region not 

 less conspicuous and important than its characteristic and lead- 

 ing groups of fishes. We might, therefore, reasonably expect to 

 find these dominant groups connected by the food relation; and 

 consistently with this expectation, we observe that the sheeps- 

 head, the cat-fishes, the suckers, and the dog-fish find an impor- 



1 Esox vermiculatus. ^Semotilus. ^Ictiobus. ^Carpiodes. 



