FISHES. 321 



in addition to the front rayed dorsal, an adipose or fatty 

 second dorsal without rays. The caudal, or tail-fin, is 

 usually in two distinct lobes, often, as in the sharks, of 

 unequal length, and usually either forked or fan-shaped, 

 convex or concave. In some of our forms, however, as the 

 rays and chimsera, there is no terminal fin, the tail ending 

 in a whip-like lash. (See fig. of Perch, p. 340.) 



The mouth of fishes is subject to more variation, both 



in position and form, than the same organ in any of the 



foregoing classes. Its position is normally in 



teeth* 1 and fr nt f the head> tte Cleft P enin g towards 

 the tail, as in the salmon. In sharks and rays, 



however, we find it beneath the head ; in the weevers it 

 is directed, like the eyes, upwards. Its shape is various. 

 In the flat-fish it becomes distorted in the adult, though 

 symmetrical in the larval form. In the sea-horse it is a 

 tube ; in the garfish, a toothed beak. In the wrasses, the 

 mouth has thick lips ; in the cods, loaches, red mullet, and 

 some of the carp family, it is supplemented by a varying 

 number of feelers or barbels. In the pike, hake, pollack, 

 and some other predatory forms, the lower jaw protrudes. 

 The tongue, which is sometimes absent, is never protruded 

 as in the other classes of animals. The teeth are usually 

 solid, and are continually being shed and renewed. In 

 size and shape they vary much, the two leading types being 

 those which are sharp and adapted to cutting and tearing, 

 and those which are flat and suitable for crushing. The 

 former belong to fishes that feed on other fish, the latter 

 to those which feed chiefly on molluscs and crustaceans. 

 In some sharks, there are hinged teeth, which are capable 

 of lying back and preventing the escape of prey ; and there 

 are, as in snakes, latent series ready to take the place of 

 those in use when the latter sustain injury. In some 

 rays, too, the teeth slant, with the inner margins cutting. 



As in other classes, the eye is, so far at least as shape 

 goes, less subject to variation than any of the foregoing 

 characters. In size, it is true,, the eyes show some differ- 



X 



