Aspect: Generally dome-shaped aggregation of colonies that form long and deep-cut valleys, which are home to the polyps' mouths. The ridges are neatly rounded and feature a very thin (sometimes invisible) groove at their summit, where septa meet. Population: Common. Notable feature: Light brown to brown with generally lighter coloured valleys. Environment: Most usually on steady substrates like rocks, but also shipreck surfaces, at depths ranging from only a few tens of centimetres down to more than 30 metres. Behaviour: Tentacles may sometimes extend during the day.
