Back bluish, turning to deep purple or almost black on the head. A pattern of 15 or more narrow, oblique to nearly horizontal, dark wavy lines in scaleless area above lateral line. Belly white. Pectoral and pelvic fins purple, their inner sides black. Body robust, elongate and rounded. Teeth small and conical, in a single series. Pectoral fins short, but reaching past vertical line from anterior margin of scaleless area above corselet. A large single-pointed flap (interpelvic process) between pelvic fins. Body naked except for the corselet, which is well developed and narrow in its posterior part (no more than 5 scales wide under second dorsal-fin origin). A strong central keel on each side of caudal-fin base between 2 smaller keels (Ref 9684).