PROCEEDINGS OF THE CALIFORNIA ACADEMY OF SCIENCES Fourth Series Vol. XXIII, No. 39, pp. 587-590, 1 text fig. august 22, 1944 No. 39 -RHINOBRYCON NEGRENSIS, A NEW GENUS AND SPECIES OF CHARACID FISHES FROM THE RIO NEGRO, BRAZIL i BY -, f GEORGE SPRAGUE MYERS Stanford University Among the fishes obtained by the late Dr. Carl Ternetz during his ascent of the Rio Negro in 1925, I have found a very interesting little tetragonopterid characin, allied to Bryconamericus, and its description is herewith presented. ; RHINOBRYCON Myers, new genus Genotype. — Rhinobrycon negrensis Myers, new species. This strange little characin forms one of the most distinctive genera of Tetragonopterinae, and one of the most easily recognized. Only three other genera of the subfamily have a projecting snout and inferior mouth, and two of these (Creagrutus and Piabina) have a peculiar, massive, three-rowed, premaxillary dentition, as well as a much heavier head. Piabarchus is more like a normal Brycon-americus in appearance, but is immediately distinguished from all its congeners by its very long anal fin, originating before the dorsal. None of the three is very similar to Rhinobrycon in appearance, but I believe that they as well as Rhinobrycon originated from Brycon-americus or from the same line from which Bryconamericus sprang. . Snout pointed in profile, projecting beyond the mouth, which is definitely inferior in position. Seen from below, the edge of the lower jaw is broadly arcuate, becoming somewhat restricted behind the point at which the maxillaries normally cover it, and the lower lip is sharp with its edge projecting horizontally, rather than ver-tically as in other characins. This lip fits up within the more ver-tically directed upper lip, which completely hides the premaxillary August 22, 1944
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