172 ANIMAL STUDIES 



162. The catfishes. Among the lowest bony fishes we 

 may place the great group to which almost all fresh-water 

 fishes belong. In this group the four vertebrae situated next 

 the head are firmly united, and by means of certain small 

 lever-like bones a connection is formed between the air-blad- 

 der and the ear of the fish, which is sunk deep in the skull. 

 The air-bladder thus becomes a sounding organ in the 

 function of hearing. The family of catfishes possesses this 

 structure, and the student should look for it in the first one 

 he catches. The catfishes are remarkable for the long feel- 

 ers about the mouth, with which they pick their way on the 

 bottom of a pond. There are many kinds the world over. 

 The small ones are known as horned pout or bullhead. In 

 these the dorsal and pectoral fins are armed each with a 

 strong, sharp spine, which is set stiff when the fish is dis- 

 turbed, and makes them very troublesome to handle. The 

 catfishes have no scales. 



163. The carp-like fishes. The still greater carp family 

 includes all the carp, dace, minnows, and chubs. They 

 have the air-bladder joined to the ear, just like the catfish, 

 but they lack the long feelers and the fin spines, while the 

 soft body is covered with scales, and there are no teeth in 

 the mouth. In the throat are a few very large teeth, which 

 the ingenious boy should find. In the sucker family these 

 throat teeth are like the teeth of a comb, and the mouth is 

 fitted for sucking small objects on the river bottom. 



164. The eels. In the great order of eels the body is 

 long and slim, scaleless, or nearly so, with no ventral fins. 

 The shoulder-girdle has slipped back from the head, so as 

 to leave a distinct neck, while ordinary fishes have none. 

 Of eels there are very many kinds some large and fierce, 

 some small as an earthworm ; and one kind comes into fresh 

 water. 



165. Herring and salmon. In the great order which in- 

 cludes the herring and salmon the vertebrae are all alike, 

 the ventral fins far from the head^ and the scales smooth to 



