Metridiidae
Metridiidae is a family of sea anemones in the order Actiniaria. Characteristics. Members of the family Metridiidae are characterised by having a mesogloeal sphincter muscle and by the mesenterial arrangement, with the mesenteries not being divided into macronemes and microcnemes. The acontia typically have microbasic b-mastigophors and microbasic amastigophors, though the latter are not always present in adults. Genera. The following genera are recognised by the World Register of Marine Species (WoRMS): Of these, "Metridium" is the most speciose while "Paraisometridium" is monotypic.