Colonies or individuals are thin and delicate. They may have only one corallite or have a prominent central corallite and widely spaced peripheral corallites. Septo-costae radiate from the central corallite like spokes from a wheel. Colour: Uniform or mottled dark browns or greens. Similar species: Superficially resembles mussids, especially Scolymia. Habitat: Lower reef slopes protected from wave action, and in crevices. Abundance: Rare but distinctive.