Smooth flower coral

Smooth flower coral is a colonial species that grows to about 50 centimetres (20 in) across. It forms a low mound of stony calcium carbonate, the surface of which is covered with tubular projections, the corallites, in groups of one to three. The polyps protrude from these and are either round or oval, with the oval form being more common at moderate depths. They are large and widely spaced and are connected by a layer of translucent, jelly-like mesoglea tissue called coenosarc which covers the surface of the carbonate skeleton. During the day they are retracted back into the cup-shaped corallites. These have large smooth-edged ridges called septa, and the polyps have corresponding grooves at their base. At night, the polyps stretch out their translucent white tentacles to feed and the coral "flowers". This coral is usually cream, yellow or pale brown, often with a green or pink tinge.