Boulder Brain Coral

Colpophyllia is a genus of stony corals in the family Mussidae. It is monotypic with a single species, Colpophyllia natans, commonly known as boulder brain coral or large-grooved brain coral. It inhabits the slopes and tops of reefs, to a maximum depth of 50 metres (164 ft). It is characterised by large, domed colonies, which may be up to 2 metres (6 ft 7 in) across, and by the meandering network of ridges and valleys on its surface. The ridges are usually brown with a single groove, and the valleys may be tan, green, or white and are uniform in width, typically 2 centimetres (0.8 in). The polyps only extend their tentacles at night.