ANALOGIES OP THE SILURINiE. 35 1 



Ageniosus,is remarkable for two things; — one^ the slight 

 excess of the tail, in regard to its length, over that of 

 the belly ; and the other, the almost total disappearance, 

 in Clupisoma, of the cirri : these two characters are pos- 

 sessed by Cetopsis ; and by these points of affinity we 

 consider they pass into each other, and close the series 

 of the SilurincB, which thus becomes, in regard to its 

 genera, a circular group. 



(286.) While the affinities we have been tracing, 

 and the forms of the genera and sub-genera, of the sub- 

 family Silurince, are still before the reader, we will 

 finish our exposition of the whole by looking to their 

 analogies. Commencing with the genera of the Silurince, 

 we find they succeed each other in the following order; 

 and by placing the sub-families of the whole group also 

 in their own series of affinity, we shall get the follow- 

 ing parallel analogical characters : — 



Genera of the 4„.,7„,^;^„i ri,„^-,^f^«.^ Sub-families of 



SiLURi>:iE. ^ the Silurid^. 



Pachypterus. Dorsal fins universally two. Pimelodin^. 



Siluras. Only one dorsal fin in the typical forms. Loricarin^. 



Cetopsis. f Eyes small or minute, placed towards the J ^^p^^^,^^ 



(^ crown. J 



Ageniosus. Body unusually compressed. Silurid^ 



Some interesting facts, connected with the general 

 structure and relations of these groups, will result from 

 a more particular exposition of these analogies ; resem- 

 blances which, we confess, did not occur to us until after 

 we had deemed it necessary to submit our arrangement of 

 the Siluridce to this test. In comparing Pachypterus 

 with the PimelodincB, we see that, throughout both 

 groups, the second adipose dorsal fin is invariably pre- 

 sent ; and that there is the strongest resemblance be- 

 tween the two is sufficiently established, by the fact of 

 all authors having hitherto actually referred them to the 

 same genus, — an error that has solely arisen from, over- 

 looking the great difference in the developement of the 



* Russell's description of his Platystachus anguillaris, vol. ii, p. 51. 



