Ophiocistioidea 海蛇函
The Ophiocistioidea is a class of extinct echinoderms from the Palaeozoic.
Ophiocistioids had a flattened dome-shaped body encased in a solid test of calcareous plates, similar to that of a modern sea urchin. The mouth was at the apex of the dome, and surrounded by a set of five jaws. The animals apparently did not have an anus, but a madreporite was on the upper surface, surrounded by what appear to be genital pores for the release of gametes.