Calcareous sponges of the class Calcarea commonly reside in tropical marine environments at more shallow regions than glass sponges. This class of sponges has fewer known species than Hexactinellida or Demospongiae with around 400 identified species. Calcareous sponges have varied shapes including tube-like, vase-like, and irregular shapes. These sponges are usually small (a few inches in height) and some are brightly colored. Calcareous sponges are characterized by a skeleton formed from calcium carbonate spicules. They are the only class to have species with asconoid, syconoid, and leuconoid forms.