Characters: This is usually an azooxanthellate species in the Mediterranean, but usually zooxanthellate on the American coast. Colonies are encrusting or nodular. Corallites are compact and slightly polygonal in outline. Septa are in two, alternating, cycles. Ten primary septa are fused with the columella. The second cycle is shorter but well developed.
Colour: Red, pink, grey or green, partly depending on the presence or absence of zooxanthellae.
Similar Species: Madracis decactis.
Habitat: Deep water.
Abundance: Rare except in caves.
Taxonomic Note: Most colonies are likely to be azooxanthellate. Indo-Pacific records require additional study.