This species is distinguished by the following characters: a robust body, elongated and rounded; teeth small and conical, in a single series; total gill rakers on first gill arch 36-42; dorsal fins 2, D1 X-XII, separated from the second by a large interspace (at least equal to length of first dorsal-fin base), second dorsal fin followed by 8 finlets; anal fin followed by 7 finlets; 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. Colour of 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, inner sides black (Ref 9684).