236 



FISHES. 



sent the limbs of other classes of Vertebrate animals. Those 

 corresponding to the arms or wings are called pectorals, and are 

 invariably fixed behind the gills ; but those which represent the 

 feet, named ventrals, may be placed either forwards, beneath the 

 throat, or more or less backwards, as far as the commencement of 

 the tail : both may differ in size, in the quality of the fin-rays, in 

 their number and structure, or one or both pairs may be want- 

 ing. Eels, for example, have no ventrals. Muraenae have neither 

 ventrals nor pectorals, and there are fishes that have no fins at all. 

 The food of fishes consists principally of animal matter. Those 

 that inhabit fresh waters live upon worms, Mollusks, the larvae of 

 water-insects, or such flies as play or alight upon the surface ; 

 others feed on reptiles and small quadrupeds. The marine kinds 

 often devour Crustaceans, star-fishes, and Mollusks, and some, 

 both of fresh and salt waters, live on vegetables. But the great 

 majority prey upon each, other the larger devouring the less, 

 these devouring others inferior to them in size, and so on. 



The armour in which most fishes are encased is well worthy of 



our admiration. In some spe- 

 cies, as the pipe-fishes and SQS.- 

 horses(Syngnatkida!) the body 

 is covered with strong bony 

 plates : these in the trunk-fish 

 (Ostracion) are so firmly sol- 

 dered together as to form a 

 box, through openings in 

 which the tail and fins pro- 

 ject. The skin of the shark is 

 covered with minute spines, 

 felt to be rough and rasp-like 

 if the hand be gently passed 

 over them from the tail to- 

 wards the head, but are imperceptible if rubbed in the contrary 

 direction. The: most common form of a fish's covering, however, 

 is that of separate scales, each embedded in a fold of the skin on 

 the margin next the head, and overlapping its successor with the 

 opposite edge. These scales vary in their form, those from diffe- 

 rent parts of the body not being quite alike even in the same fish. 

 The characters available for the classification of fishes are thus 

 derivable from very various sources, as will be seen in the follow- 

 ing tabular view of their arrangement, according to the system 

 adopted by Cuvier : 



FIG. 245. SCALES OF FISHES. 



