Calcarea is the only class with asconoid and syconoid construction. All others have leuconoid construction. The calcium carbonate spicules are only megascleres, or large structural spicules. Other groups of sponges have microscleres, which are smaller reinforcing spicules. Most Calcarea are 10 cm less in height, and are dull in color, although some colorful species are known.
Other Physical Features: ectothermic ; heterothermic