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.
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- sessile
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non-motile; permanently attached at the base.
Attached to substratum and moving little or not at all. Synapomorphy of the Anthozoa