These colonies are found in deep water (usually below 20 m) and can form very large (> 1.5 m), lettuce-like colonies. or flat or spreading plates.

Corallites develop roughly concentric rows. The individual corallites are very small, and are located on the side of the valley nearest the middle of the colony, thus they face outwards. This is most clear in valleys nearest the periphery of the colony. Ridges are usually squared rather than rounded or pointed.

Colour is usually dark, and is shades of brown or green, with reddish tints.