; phylum Cnidaria, class Anthozoa)
A subclass of sedentary, colonial corals with polyps that always have eight tentacles which are almost invariably pinnate. There are eight complete, unpaired mesenteries and septa, and a ventral groove on the stomodaeum. Skeletal structures are usually made from calcareous spicules.
Subjects: Earth Sciences and Geography — Zoology and Animal Sciences.