FISHES. 317 



on reptiles and small quadrupeds. The marine 

 kinds often devour crustaceans, star-fishes, and mol- 

 lusks, 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 de- 

 vouring 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 species, as 



FlG. 245. SCALES OF FISHES. 



the Pipe-fishes and Sea-horses (Syngnatliidse) the body 

 is covered with strong bony plates : these in the 

 Trunk-fish (Ostraciori) are so firmly soldered together 

 as to form a box, through openings in which the tail 

 and fins project. 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 towards 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 imbedded 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 different 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 following 

 tabular view of their arrangement, according to the 

 system adopted by Cuvier : 



