196 CLASSIFICATION OF FISHES. 



box^ and from the plates bywhichit is covered resembling,, 

 in shape^ those of the chelonian reptiles, or tortoises. 

 They are all fish of a small or moderate size^ with rather 

 large eyes ; but very small mouths^ armed with a few 

 conical and real teeth : so different is their internal 

 structure from that of the osseous fishes, that M. Cuvier 

 confesses that the greater portion of their vertebrae are 

 cemented together ; and the ribs exist only in a rudi- 

 mentary state. They have no ventral fins^ and they 

 have but one dorsal. This evident inferiority to the 

 BalistincB at once shows them to be the sub-typical 

 group. Some of the species are furnished with 

 horn -like protuberances^ giviiig them a very grotesque 

 appearance; and all are so compactly covered with the 

 impenetrable and immoveable cuirass of the body, that 

 they have only the power of moving the tail, the fins, 

 and the thin lips of their little mouth. Most of the 

 species are found in the Indian seas. 



(173.) We now^ come to the aberrant group, composed 

 of the TetraodincE, the Diodonince, and the Cephalina: 

 these three are distinguished from the former by having 

 no true teeth, these processes being supplied by certain 

 lamina of an ivory substance placed inside of the jaws.* 

 They are also entirely destitute of the squamular plates; 

 their body being covered with a simple skin, which is 

 either rough or beset with spines. In other respects 

 they have a general resemblance, both in shape and 

 structure, to the other cheloniform fishes; the dorsal fin, 

 however, is invariably single. A prejudice against 

 eating these fish seems to be prevalent in all the coun- 

 tries w^here they are found, and also a general belief that 

 most of the species are poisonous. 



(174.) The TetraodincB t> or hare-fish (^Tet. diade- 



* M. Cuvier remarks, that these laminee of the jaws are essentially true 

 teeth, united together and succeeding each other as they are successively 

 worn out by the efiFect of triturition. If this be true, which there seems no 

 reason to doubt, it reveals an absolute point of analogy to the gliriform 

 quadrupeds, where the cutting teeth are renovated nearly in the same 

 manner. 



f It seems advisable to designate this group as the TetraodincE ; the 

 Tetrao7ii7iiS being a sub-family of rasorial birds. 



