Blue Hamlet

Hypoplectrus gemma has a deep body which is markedly compressed laterally. It has a straight forehead and a rather short snout which has a protrusible top jaw The preoperculum is angular and has serrations along its edges and a number of small spines which point to the head on its lower edge close to the angle. The dorsal fin has ten spines and 14-17 soft rays and is continuous. It has long pelvic fins which extend as far as, or beyond the anus. The caudal fin is slightly forked. The head, body and fins of this species are plain iridescent blue and there is a black stripe on the upper and lower edges of the caudal fin. This species has a maximum recorded length of 13 centimetres (5.1 in), although the method of fish measurement used was not given.

Hypoplectrus gemma is found in the western Atlantic Ocean. It was considered to be endemic to Florida but it has since been discovered off the Yucatan Peninsula in Mexico, It has also been found in the Dutch West Indies off the island of Bonaire. It has also been recorded on the northern Bahamas and in Cuba.