128 CLASSIFICATION OF FISHES. 



that both should turn almost upon their backs^ in order 

 to seize their prey. The teetli of the shark exhibit, 

 perhaps, the most formidable apparatus for devouring, 

 of any animal in creation. In some species they are 

 so numerous, that, upon opening the mouth, the eye 

 sees nothing but a forest of pointed teeth, any one of 

 which, if detached, "vvoiild be sufficient to inflict a most 

 severe wound : some of these are for the purpose of 

 seizing, others for tearing; but there are none for grind- 

 ing, as the food of the shark is always swallowed in an 

 entire state : the only exceptions to this general rule are 

 found in those genera (^Pristis and Mustelus) which 

 form the passage to the rays, and where the teeth are 

 flat, blunt, and tesselated. All the other sharks have 

 pointed teeth, but differently modified in their form ; 

 and this diversity, as implying difference of food or 

 habit, deserves much attention. The gill- covers, as 

 already observed, do not open as in ordinary fishes : the 

 branchia, in fact, are completely concealed beneath the 

 skin ; yet their number may be judged of by certain 

 oval perforations, placed in a single row on each side, 

 through which the water is emitted in the act of respir- 

 ation. Let us now proceed to examine this family in 

 more detail. 



(114.) To professor Rafinesque* belongs the honour 

 of being the first who ventured to break up tlie old 

 Linnsean genus Squalus into a number of others ; to all 

 of which he has attached well-constructed names, and, 

 in most cases, very satisfactory descriptions. This re- 

 formation was begun many years before the appearance 

 of the Regne Animal; but the name and works of Ra- 

 finesque were then so httle known, that M. Cuvier was 

 ignorant that nearly all his divisions had been anticipated. 

 As the work wherein these genera were first charac- 

 terised, is now become scarce, and as Rafinesque's names 

 have the undoubted priority of all others, we shall here 

 lay them before the reader in his OTvn words, more par- 

 ticularly as he describes two or three which stiU re- 

 * Caratteri di Alcune Nuovi Generi, &c Palenno, 1810. 



