212 CLASSIFICATION OF FISHES. 



ones in their respective circles which have the branchial 

 aperture unusually large ; both have the body much 

 lengthened ; both have the gill membrane either with- 

 out any rays^ or with merely a single pair ; in both, 

 the caudal fin surrounds the extremity of the spine, and 

 (what is very remarkable), in both these types, the 

 upper portion of the caudal is longer than the lower. 

 Polypterus is not more unlike the other cheloniform 

 fishes, than Acipenser is unlike the rays and the sharks ; 

 and yet the latter affinity has been universally acknow- 

 ledged. Unfortunately, however, we cannot make out 

 whether M. Geoffrey's original memoir on Polypterus, 

 which we have not the means of consulting, mentions 

 any thing of the nature of the skeleton : if this is truly 

 sub-cartilaginous, the question, we think, would be at 

 once decided ; but if it is osseous, the probabihty is 

 diminished of this perplexing type entering into the 

 present order. There is, indeed, an evident — though, 

 we think, a distant — resemblance between the form of 

 Polypjterus and some of the Siluridce, — a resemblance 

 which results from the one, apparently, representing the 

 other, as will be seen in the following comparison : — 



Familiefi of the Plectognathes. Families of the Malacoptertges. 



Balistid^. Pleuronectidce. 



Chironectida;. Sahnonidce. 



Lophidce. Cohitidce. 



Potypteridce (?). Siluridcs. 



SyngnathidcE . GadidcB. 



But it is not necessary to prolong this discussion ; and 

 we shall, therefore, at once proceed to the next order. 



CHAP. VIII. 



ON THE APODES, OE ANGUILLirORM FISHES. 



(185.) The fishes belonging to the Linneean order of 

 ApodeSj — a name which we shall now revive, — are not 



