The Calcareous sponges belong to the Class Calcarea and are characterized by spicules made out of calcium carbonate (calcite). If one were to look at a poriferan spicule under the microscope, it might resemble the mercedes_bens emblem. Indeed, this is how the spicules in Calcaerous sponges look. However, instead of the common three-pointed star shape, Calcaerous spicules can be four-pointed.

All sponges in this class are strictly marine dwellers. All three body plans are represented within class Calcarea : asconoid, syconoid, and leuconoid. Typically, Calcaerous sponges are very small, ranging from 3-4 inches in height. Of the 15,000 or so species of Porfiera that exist, 150 of those are Calcaerous.

Calcareous sponge is a class of the Phylum Porifera. The species of Calcarea varies from radial symmetrical vase shaped body types to colonies made up of a reticulum of thin tubes or irregular massive forms. Calcareous sponges are generally characterized by their endoskeleton made up of spicules, they are sedentary filter feeders, and lack any real tissues. Calcareous sponges are most commonly found in shallow tropical waters. Generally, Calcarea are small sponges. The different shapes of calcareous sponges are relatively simple, either purse, vase, pear or cylinder-shaped. And the skeleton has a either a mesh or honeycomb structure. Unlike most other sponges, calcareous sponges lack hollow canals, which makes the sponge stronger.