OCR Text |
Show 1871.] FRESHWATER SILUROIDS OF INDIA. 705 Genus MACRONES, Dumeril. 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 m y 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. 11; M. carcio, A. 12-13; M. tengana, A. 14; M. batasio, A. 16; whilst the Pseudobagrus aurantiacus 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 denote other internal structural differences in those which I have examined. 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 vertebras, 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 posterior extremity of the 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 transverse 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. pl. 23. f. 60. D.J|0. P. |. V. 6. A. g. 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-fo 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 ba^e 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 Society of Bengal,' September 1871. |