Some are encrusting but others are hummocky or have thickened sections, with plates, whorls or tiers which tend to lie parallel to the underlying surface.

The corallites (stony cups in which the polyps sit) are usually level with the surface but may be protuberant in some colonies.

This coral is usually some shade of brown, green or red, sometimes with the oral discs of the polyps being a contrasting colour.

Its range extends from the Red Sea and Madagascar to Japan, Australia and many Pacific island groups.

[2] Corals are principally threatened by habitat loss due to the destruction of reefs and by global warming.