POLYNEMIDAE Polydactylus microstomus, 9.9 cm SL (from Ambon, Indonesia; photo by Seishi Kimura) Polydactylus microstomus (Bleeker, 1851) Smallmouth Threadfin D VIII+I, 12-14, 9; A III, 11-12; P1 13-14+5 filaments; LLp 46-49; GR 24-33. Body moderately deep, compressed. Posterior margin of maxilla reaching to or slightly short of a vertical through posterior margin of adipose eyelid. Lip on lower jaw welldeveloped, dentary teeth restricted to dorsal surface; teeth villiform in broad bands on palatines and ectopterygoids; vomerine tooth plate covered with skin and teeth absent; palatines inwardly turned anteriorly. All pectoral-fin rays, except uppermost 1 or 2, unbranched. Longest pectoral filament just short of or extending slightly beyond posterior tip of pectoral fin. Swimbladder present, well-developed. Color: a large black spot anteriorly on lateral line. Pectoral-fin membrane yellowish; pectoral filaments faintly white. Anterior margins and origins of pelvic and anal fins faintly white, remaining parts yellow. Size: maximum length 16 cm SL. Distribution: distributed in the eastern Indian and western Pacific Oceans, from India east to Taiwan and New Caledonia. Not occur in Australian waters. Remarks: inhabiting turbid coastal waters, estuaries and mangrove creeks, as well as mangrove-lined rivers.