The Food of Fresh-Water Fishes. 455 



them Chironoraus and a fourth ephemerid larvae), the relative 

 insignificance of Crustacea (about ten per cent., — nearly all 

 Entomostraca), and the practical absence of Vermes and Pro- 

 tozoa are the remaining salient features of the food characters 

 of this family. 



FAMILY SILURID^. 



The family of catiishes taken together is nearly omnivorous 

 in habit, and their alimentary structures have a correspondingly 

 generalized character. The capacious mouth, wide oesophagus, 

 and short broad stomach, admit objects of relatively large size 

 and of nearly every shape; the jaws, each armed with a broad 

 pad of fine sharp teeth, are well calculated to grasp and hold 

 soft bodies as well as hard; the gill-rakers are of average 

 number and development; and the pharyngeal jaws — broad, 

 stout arches below and oval pads above, with thin opposed 

 surfaces covered with minute, pointed denticles — serve fairly 

 well to crush the crusts of insects and the shells of the smaller 

 mollusks and to squeeze and grind the vegetable objects which 

 appear in the food. The use made of the jaws in tearing mol- 

 lusks from their shells, as described further on, is probably the 

 most peculiar feeding practice of these animals; and the indif- 

 ference of several of the species to the past history or the present 

 condition of their food, distinguishes them as the only habitual 

 scavengers among our common fishes. 



The family is a very abundant and characteristic one in 

 this region. It ranges in size from the smaller species of 

 Noturus, only an inch or two in length, to monsters more than 

 two hundred pounds in weight; and inhabits every kind of water 

 from the greatest rivers of the continent to small temporary 

 ponds of surface water, where its presence is the staiiding won- 

 der of the fisherman and the naturalist. 



In Illinois we have three genera and twelve species of these 

 fishes, as at present classified, none of them unfit for food 

 except the smallest ones, and two or three of them the equals 

 of any river fish. 



