Colonies are flat (foliaceous or encrusting), massive or branching. Massive colonies are spherical or hemispherical when small and helmet- or dome-shaped when large, and are commonly over 5 m in diameter. Corallites are small, immersed, with calices less than 2 mm in diameter and filled with septa. Polyps are usually extended only at night (Veron, 1986). Corallites often very small (<2 mm across), but colonies very large. Colonies domed; can reach up to 8 m in height (Richmond, 1997).