Characters: Colonies are encrusting to massive, less than 0.2 metres across. Most consist of a small number of encrusting corallites. Corallites are plocoid. Septo-costae are prominent and have thick teeth which have ornamented edges. Columellae are deep seated. Colonies lack the fleshy tissue of most Acanthastrea. Colour: Mottled browns. Similar species: Acanthastrea faviaformis resembles the faviid genus Favia more than any other Acanthastrea and has been called Favia matthaii in other publications. See also A. regularis. Habitat: Shallow reef environments. Abundance: Uncommon.