This coral can be found in several forms: large masses, tall branching forms, and encrusting various types of shells. These different forms grew in response to differences in wave energy in an environment. For example, the encrusting form grew where wave energy was high, since any large branching form that grew would be toppled over. Fossil corals are white, though they were doubtless colorful like today’s corals when they were alive.
M. J. O'Donnell