1871.] FRESHWATER SILUROIDS OF INDIA. 705 



Genus Macrones, DumeVil. 

 Pseudobagrus, Bleeker. 



This genus possesses about twenty known representatives on the 

 continent of India and in Burmah ; but previously to describing some 

 individuals I will give my reasons for considering Pseudobagrus a 

 synonym of Macrones. 



The genus Macrones includes species with less than twenty rays 

 in the anal fin ; Pseudobagrus those possessing twenty or upwards, 

 the other differences being : — in the first the dorsal fin has one spine 

 and seven rays ; in the second, one spine and from five to seven rays. 



If we examine the species, we see amongst them the following : — 

 Macrones keletius, A. 9 ; M. leucophasis, A. 10 ; M. cavasius, A. 1 1 ; 

 M. carcio, A. 12-13; M. tengana, A. 14; M. batasio, A. 16; 

 whilst the Pseudobagrus auranliacus has A. 20-22 ; P. vachellii, 

 A. 23-24 ; P. chryseus, A. 27, — thus showing a regular gradation. 



The subgenera, or those with a separate interneural shield on the 

 nape and those destitute of such, appear, at least sometimes, to de- 

 note other internal structural differences in those which I have exa- 

 mined. Amongst the former are M. aor and M. lamarrii, in which 

 the anterior portion of the air-vessel is attached to the under surface 

 of the bodies and expanded processes of the anterior vertebrae, but 

 its posterior extremity is elongated and pyriform ; internally it has 

 a longitudinal septum. 



On the contrary, in those not having this separate shield, the pos- 

 terior extremity of tire air-vessel is not elongated, the longitudiual 

 septum (as in all those of this genus which I have examined) has a 

 communicating opening anteriorly ; and sometimes there are trans- 

 verse partitions forming chambers, which freely communicate with 

 those on the same, and by means of the anterior one with those on 

 the opposite side, as in M. cavasius, M. tengara, M. carcio. 



Amongst the species of this genus are several but slightly known, 

 and others which I believe have been erroneously identified. 



Macrones carcio, H. B. pi. 23. f. 60. 

 D.||0. P.|. V. 6. A.|f . C.19. 



The figure in the ' Gangetic Fishes' marked Pimelodus batasius 

 belongs to this species. In Hamilton Buchanan's MS. drawings* 

 is a figure of the latter 3-j^j- inches long, showing, as he observes in 

 the text, that none of the barbels are as long as the head. 



Groove on the summit of the head extends to midway between 

 the posterior edge of the orbit and the base of the occipital process. 



Fins. Dorsal spine slightly serrated anteriorly in its upper third 

 and also along the whole of its posterior surface, its length being 

 equal to half that of the head ; the adipose fin commences some 

 distance behind the first dorsal, and the extent of its base is from 



* Concerning identifications of Hamilton Buchanan's MS. drawings and the 

 British -Museum Catalogue, see article in the 'Proceedings of the Asiatic So- 

 ciety of Bengal,' September 1871. 



