Colonies are phaceloid; corallites are closely compacted, 20-40 millimetres diameter. Small solitary polyps are common. Primary septa are very exsert and are conspicuous underwater. First and second order septa plunge steeply near the centre of the corallite. There are no columellae. Polyps have large tubular tentacles with knob-like tips.
Usually pale grey or green, with distinctively coloured tips to the tentacles.