coral Corals are marine invertebrates within the class Anthozoa of the phylum Cnidaria. They typically form compact colonies of many identical individual polyps. Coral species include the important reef builders that inhabit tropical oceans and secre ...

s, a septum (plural septa) is one of the radiating vertical plates lying within the

corallite A corallite is the skeletal cup, formed by an individual stony coral polyp, in which the polyp sits and into which it can retract. The cup is composed of aragonite, a crystalline form of calcium carbonate, and is secreted by the polyp. Corallit ...

wall. Outside the corallite wall these plates are known as

costae In vertebrate anatomy, ribs ( la, costae) are the long curved bones which form the rib cage, part of the axial skeleton. In most tetrapods, ribs surround the chest, enabling the lungs to expand and thus facilitate breathing by expanding the c ...

(singular costa). The septa may be thick, thin or vary in size. They may have teeth which range from needle-like to blade-like and are often characteristic of different genera.

References

{{reflist Cnidarian anatomy