Leuciscus. INDIAN CYPRINID^. 403 



The effect of the foregoing definition, the substance of which may be ex- 

 pressed in a few words, as in the synopsis, is to exclude Cyp. boga, Buch. 

 Cyp. ariza, id. Cyp. sopJiore, id. and Cyp. danrica, id. from this genus, though 

 referred to in the Regne Animal as Leucisci. The two first are Gudgeons, the 

 third is a Systomiis, and the fourth is a Perilamp, thus reducing the seven 

 Indian species of this genus indicated by Cuvier to three. But in place of those 

 removed we must add Cyp. cocsa, Buch. as its alimentary canal scarcely 

 exceeds the length of the body, while that of the Barbels, with which it stands 

 in the Regne Animal, varies from three to six times that length ; it is besides 

 without the dorsal spine of the Barbels, while it has faint bars across the body, 

 indicating an approach from the Leucisci to the Opsarions. Six other species, 

 most of which I have carefully examined, must also be added, making the 

 number of our Indian Leucisci already known amount to ten. 



The improvement, if there be any in this restriction of a genus acknow- 

 ledged before to be imperfect, must rest a good deal on the principle, that 

 nature in fixing the position of the dorsal fin, determines from this, what shall 

 be the concurrent habit and structure of the species. 



In looking over the descriptions of the six European Leuciscs whose 

 dorsal is opposite to the ventrals, we find the anal small, and the mouth low 

 and horizontal, as if exclusively formed for obtaining their food from the 

 bottoms of waters, and we know this to be further confirmed by the fact of 

 their subsisting chiefly on herbage and worms. We then arrive at Cuvier's 

 second division of this genus, in which the dorsal is placed behind the ventrals. 

 Now, when the dorsal is placed so far behind the ventrals as to be opposite to 

 the anal, I no longer regard the species as Leuciscs, but Perilamps or Opsari- 

 ons, according as they correspond in most respects with one or other of those 

 genera. If we take the Rudd {L. erythroptlialmus) as an example, we find it 

 is marked by the receded position of the dorsal, the greater development of 

 the anal, the upturned mouth, and the remarkable brilliancy of colours, all 

 denoting an affinity to the Perilamps ; which is further confirmed by a cor- 



