These are the sponges with calcareous (rather than siliceous) skeletons. Their spicules are made up of calcium carbonate; they are simple in structure or may have up to four rays. Members of the Class Calcarea are small. All species are marine.
non-motile; permanently attached at the base.
Attached to substratum and moving little or not at all. Synapomorphy of the Anthozoa