Characters: Colonies are massive, forming large rounded domes or columnar, becoming plate-like at edges. Corallites are flattened, not heavily calcified, of similar size, 2-3mm diameter, formed by extratentacular budding. Septa are in two unequal orders, first order septa forming a small columella. Walls are thin, H507with regularly dentated thin costae.
Colour: Brown, grey or yellowish-green.
Similar Species: Orbicella annularis is very similar with more columnar colonies and corallites have thicker walls. Orbicella franksi has larger, conical corallites of unequal sizes and septa of similar size. Paramontastraea salebrosa and Astrea curta have corallites of similar size; the latter has similar morphological variations. See also Favia stelligera.
Habitat: Reef habitats.
Taxonomic Note: Well-defined species formerly in genus Montastraea (for history refer to Weil and Knowlton, 1994). However, neither the description nor the holotype of the original Ellis and Solander (1786) species are recognisable. Although this name is technically meangless it should be accepted on the basis of unambiguous usage (see 'Overview of coral taxonomy'.