The spotfin killifish (Fundulus luciae) is a member of the genus Fundulus. It closely resembles the mummichog in shape and coloration, but the two species can be distinguished by dorsal ray count; 8 in the spotfin, 11 or 12 in the mummichog. The dorsal fin of the spotfin originates farther back, over or slightly behind the anal and about equidistant between the top of the tail and the anterior half of the eye.