Gorgonia

Gorgonia is the best-known genus of the Axifera (q.v.), a group of the Alcyonaria (q.v.), or corals, with an eight-rayed symmetry. Its most familiar ally is Corallium, the "red coral" of commerce, from which it mainly differs by the facts that the corallium is formed from the external layer or ectoderm by means of an ingrowth (invagination) around the base; in Corallium the skeleton is formed by the "mesogleea" (q.v.) or the middle layer of tissues. The colony is fixed and branched. There is no "polymorphism" (q.v.), all the individual polypites being built on the same plan. In addition to the central axial skeleton, there are numerous spicules scattered through the external tissues. They are all marine. Spicules referred to the allied genus Gorgonella have been described from the Miocene, while some, probably belonging to Gorgonia, occur in Tertiary rocks in Trinidad.