346 



CLASSIFICATION OF FISHES. 



term, where the cirrci are fully developed. In other re- 

 spects, the general form of Ageniosus and Silonia are very 

 dissimilar. In the latter the head is short and thick, but 

 very slightly widened or flattened : the whole fish, in- 

 deed, is much compressed, and the lower edge, as Dr. 

 Hamilton says, is " sharp, somewhat like a knife," or, 

 in other words, carinated : the mouth is moderate ; the 

 eyes are large ; and the whole appearance of the other 

 parts is more in accordance with ordinary fishes than 

 with any of the present family. One species is dia- 

 phanous *, the viscera being inclosed in a bright silver- 

 coloured membrane, analogous to that of Argentina: 

 the two cirri are even more minute than in the last, 

 being scarcely visible without the aid of a magnifier ; 

 and in both these speces the gill membrane has nume- 

 rous rays. As the other subordinate types of this genus 

 remain to be determined, we shall hazard no conjectures 

 upon them, but at once proceed to the next, which we 

 propose to designate Pachypterus. In this there is still a 

 second adipose dorsal fin, but the cirri are very conspicuous ; 

 and the tail is considerably more lengthened, so as to 

 be often near three times the length of the abdomen : it 

 is bordered beneath, for nearly its whole extent, by the 

 anal fin. We cannot, at present, determine more than 

 two of the sub-genera belonging to this group; — one from 

 India, which is the typical, includes many species ; the 

 other, which is the Hypopthalmus of Spix (Jig, 86.), and of 



which two are known, seems peculiar to the rivers of Ame- 

 rica. The second dorsal fin is reduced to so small a size, 

 that it becomes almost obsolete. We next pass to the genus 



* Chandramara, lb. p. 162. 



