Paleeozoic group, the Rugosa (q.v.). It is, however, now regarded as an ordinary Astrean coral.
Historical reference: Do not rely on this information. It is very old. About this collection
Holocystis, a genus of corals found in the Lower Greensand of the south of England. The genus is well-known, owing to the fact that the septa are arranged in multiples of four instead of six, and so it was for long included among the