GOBIIDAE Acentrogobius caninus, 6.0 cm SL (photo by Koichi Shibukawa) Acentrogobius caninus, 6.5 cm SL (photo by Ukkrit Satapoomin) Acentrogobius caninus (Valenciennes, 1837) Tropical Sand Goby D VI+I, 9; A I, 9; P1 18; LR 26-27; PDS 16. Body moderately elongate and compressed. Head slightly compressed; jaws subequal; gill opening not extending anteriorly to a vertical through posterior margin of preopercle; single or some enlarged caninoid teeth on each side of lower jaw; tongue truncate. Pelvic fins united medially; frenum present. Scales ctenoid, excluding those on nape, pectoral base and breast cycloid; no scales on cheek; operculum may be scaled. Sensory canals and pores present on head; longitudinal pattern of sensory-papillae rows on cheek; aggregation of sensory papillae just behind chin. Color: large ovoid black spot just above dorsalmost of gill opening; 4 midlateral dusky spots on body. Size: 13.0 cm. Distribution: Indo-West Pacific. Remarks: found in tidal estuaries with sandy-mud bottom.