Characters: Colonies are usually columnar. The columns are club-shaped, sometimes divide, and are slightly flattened in section. Corallites are widely separated, circular in outline, with a solid conical columella. Eight primary septa are distinctive. The coenosteum has fine spinules. Colour: Usually green with yellow oral discs. Similar species: Madracis decactis and M. mirabilis, both of which have 10 primary septa. Habitat: Lower reef slopes protected from wave action. Abundance: Uncommon.