SILURUS. THE SUB-GENERA. 353 



follows that, if Silonia had not been discovered, we 

 should have had no precise representation of Cepola and 

 all the other riband-like fishes ; so that, under this view 

 of the subject, what appeared to be an anomalous form 

 among the Silurin(S, turns out to be one almost neces- 

 sary to preserve that system of representation, and that 

 uniform variation of structure, we trace in aU the other 

 groups. 



(287.) As we have already shown that the primary 

 divisions of the whole family represent the primary 

 order of fishes, we need not submit the genera of the 

 SilurincE to the same test; because, if they represent, as 

 we think we have now proved they do, the sub-famihes 

 of their own circle, their analogy to the orders becomes 

 established. We shaU, therefore, now call the reade/s 

 attention to the different sub-genera of the restricted 

 genus SiluruS) in order to inquire whether these suh- 

 genera do not, in the same manner, represent the genera 

 of the sub-family; the affinities of these sub-genera have 

 already been explained. We shall now, therefore, glance 

 at their analogies. 



The sub-genera of Silurus have been The genera of the SilurincB as already 



. seen to follow each other thus — stated, stand in the following order — 



Callichrus. Pachypterus. 



Silurus. Silurus. 



yialapturus. Plotosus. 



Pusichthys. Cetopsis. 



Clupisoma. Age:miosus. 



Our proposition is, that each of these divisions are 

 mutual representations of each other, independent of all 

 those affinities by which the contents of each separate 

 series are united ; and we shall now endeavour to sub- 

 stantiate its truth. In the first place, we see Callichrus 

 standing opposite to Pachypterus ; and we find that both 

 have the body brightly coloured, and the caudal fin 

 lobed, in contradistinction to Silurus, where the colours 

 are dark and lurid, and the caudal fin rounded. That 

 there is the strongest resemblance between Malapturus 

 and Plotosus, may be established by the authority, if 

 authority is required, of Bloch, who places them close 



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