THE FISHES 168 
156. The catfishes.—Lowest of all the 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-bladder 
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. 
15%. 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. 
158. 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. 
159. Herring and salmon.—lIn the great order which in- 
cludes the herring and salmon the vertebre are all alike, 
the ventral fins far from the head, and the scales smooth to 
