33-i CLASSIFICATION OF FISHES. 



other. As the SiluridcB are the most mailed of all the 

 soft-finned fishes,, they thus become analogous to the 

 tortoises, or chelonian reptiles, and to the cheloniform 

 fishes ; hence it is natural to suppose that the Lori- 

 carina, from being the most mailed, are those which 

 should stand at the head of the family. On the other 

 hand, the Pimeloduue, in point of general structure, 

 appear to be the most perfectly formed, or, rather, the 

 most highly organised, of the two : their body, indeed, 

 is naked, but they have all two distinct dorsal fins ; and 

 those cirri, which are few and short, or altogether want- 

 ing, in the Loricarince, are here developed to an enor- 

 mous length, more especially in those of the New World. 

 Leaving these, we may proceed to the other comparisons, 

 where the analogies are so strong that they must strike 

 every one who has paid any attention to this most fas- 

 cinating department of zoology. The SilurincB, indeed, 

 are not, like the eels, destitute of the ventral fins, for 

 then they would actually become apodal fishes ; but 

 the great development of their tail, their rounded 

 caudal fin, their dark lurid hues, and their natural 

 habits, leave nothing more to be desired on this head. 

 It is proper, also, to observe in this place, that what has 

 previously been said on the habits of the European 

 species (Silurus giants), must be looked on as more par- 

 ticularly applicable to this division, rather than to the 

 other sub-family of the Siluridaj about which, in fact, 

 we really know little or nothing. The analogy between 

 the Aspredince and the Plectognathes is rendered per- 

 fectly conclusive by the structure of the gill-covers, 

 which in these two groups are immoveable. Again, it 

 may be observed as a general rule, that, on comparing 

 any natural group of fish with the primary orders of the 

 class, we shall almost invariably find that those whose 

 eyes are small, and situated at the top of the head, turn 

 out to be the most aberrant in their own circle : now, 

 this is explained by looking to the order Plectognathes, 

 where we find both the Balistidce and the Chironectidce 

 possessing this structure in a remarkable degree. The 



