NOTES ON MEGALOBRAMA AMBLYCEPHALA,SP.NOV.,A DISTINCT SPECIES FROM M.TERMINALIS(RICHARDSON)

Most ichthyologists working on Chinese fresh-water fishes have been inclined to accept that there is only one single valid species of the genus Megalobrama throughout our mainland, i. e., M. terminalis (Richardson). However, recent study on Megalobrama at Liang-Tse Lake, Hupeh Pro-vince, revealed the coexistence of a distinct species, for which the name M. amblycephala, sp. nov. is proposed. The new species can be distinguished externally from M. terminalis by the contour of the head and shape of the mouth opening, by the relative height of the dorsal fin, and by the proportion between height and length of the caudal peduncle. Internally the differences are even more pronounced. In contrast to M. terminalis, the new species consistently has more verte-brae and ribs to its vertebral column, and its supraorbital bone, besides being much thinner, is semilunar in outline instead of rectangular. The largest chamber of its air-bladder is the middle one instead of the ante- rior. The gill rakers on its first gill arch are always fewer by 5—6, and scarcely lamellate in form. Examination made on large number of specimens, of vatious sizes and both sexes, has clearly eliminated the possibility of these divergences being due to sex dimorphism or individual variation.