madrepora

from The Century Dictionary.

• noun The typical genus of Madreporidæ, containing some of the commonest madrepores, of various branched shapes, among them some of the most extensive reef-building corals. M. cervicornis is a species so called from its branching like the antlers of deer.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Zoöl.) A genus of reef corals abundant in tropical seas. It includes than one hundred and fifty species, most of which are elegantly branched.