Calcispongiae
The calcareous sponges of class Calcarea are members of the animal phylum Porifera, the cellular sponges. They are characterized by spicules made out of calcium carbonate in the form of calcite or aragonite. While the spicules in most species have three points, in some species they have either two or four points. Calcareous sponges vary from radially symmetrical vase-shaped body types to colonies made up of a meshwork of thin tubes, or irregular massive forms. The skeleton has either a mesh or honeycomb structure.
Hyalospongiae
The accepted name for Hyalospongiae is Hexactinellida. Hyalospongiae are sponges with a skeleton made of four- and/or six-pointed siliceous spicules, often referred to as glass sponges. They are usually classified along with other sponges in the phylum Porifera
Demospongiae
The Demospongiae are the largest class in the phylum Porifera. In fact, the demosponges include 81% of all species of sponges with nearly 7,000 species worldwide. They are predominantly leuconoid in structure. Their "skeletons" are made of spicules consisting of fibers of the protein spongin, the mineral silica, or both. Where spicules of silica are present, they have a different shape from those in the otherwise similar glass sponges. Members of the Demospongiae are asymmetrical. Sponges are unlikely to be eaten by other animals due to their unpleasant taste. However, some organisms are able to subsist on sponges, and others live with them as symbionts. Some sponges harbor photosynthetic bacteria, while some serve as protection for other organisms.