The Halfblack triplefin (Enneapterygius hemimelas), also known as the Half-black triplefin, Blackbelly triplefin, or the Green-tail threefin, is a species of triplefin blenny in the genus Enneapterygius. It was originally described by R. Kner and F. Steindachner in 1867. It is a non-migratory tropical blenny known from coral reefs in the western P...