Identified by the four bony protuberances on the top of the head (the protuberances are smaller in females and young and absent in the freshwater form), the chainlike lateral line, the sharp spines on the preoperculum, and the absence of palatine teeth (Ref. 27547). Gill rakers reduced to rounded, spiny protuberances (Ref. 27547). Soft dorsal often much enlarged in adult males; caudal truncate to slightly rounded (Ref. 27547). Young gray above, with three or four dark saddles below dorsal fins and a dark spot on dorsal side of caudal peduncle; adults are darker; spiny dorsal fin dusted with black; soft dorsal, anal, pectoral and caudal fins have dark bars; pelvic fins pale (Ref. 27547).