Zoantharia

Zoantharia, a subclass of the Actinozoa or Anthozoa (q.v.), including those in which the tentacles are simple, arranged in one or more circles; the number of the mesenteries and tentacles is generally either six or a multiple of six, and never of eight or some multiple of eight as in the Alcyonaria. It includes three groups -- the Actiniaria or Sea-Anemones, the Antipatharia or Black Corals, and the Madreporaria or True Corals. They are all marine.