Soft coral which builds mushroom or toadstool-shaped colonies of up to 50 cm in diameter with many polyps on the top. In some species the margin of the hat is warped. There are two forms of polyps: autozoids which are more than 1 cm tall, have 8 feathered tentacles and can retract completely; siphonozoids being tiny tube-like regressed polyps which are responsible for the intake and release of water. The body of the colony is sustained by calcareous pins, called spicules. The colour of the body may be white, yellow, brown or green. Polyps are of the same colour but in some species the autozoids are white.