Characters: Colonies are laminar or subarborescent, with these different growth-forms characteristically occurring together in large colonies. Valleys are short, straight, and spread in a fan before dividing. They radiate from the colony centre on flat surfaces, but are highly contorted on branches. Flat surfaces often have concentric growth lines. Tentacles are extended only at night. Well developed colonies always have some branch development. Colour: Blue or pale brown with blue margins (which may photograph pink). Tentacles are extended only at night. Similar species: Merulina ampliata, which has thicker and coarser skeletal structures. Habitat: A wide variety of reef environments, especially lagoons and upper slopes. Abundance: Common.