Metridiidae is a family

Family (biology)

In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...

 of sea anemone

Sea anemone

Sea anemones are a group of water-dwelling, predatory animals of the order Actiniaria; they are named after the anemone, a terrestrial flower. Sea anemones are classified in the phylum Cnidaria, class Anthozoa, subclass Zoantharia. Anthozoa often have large polyps that allow for digestion of larger...

s in the order

Order (biology)

In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...

 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

Acontia

Acontia is a genus of moths of the Noctuidae family.-Species:* Acontia albida * Acontia albinigra Warren, 1913* Acontia antecedens Walker, 1869* Acontia antica Walker, 1862* Acontia apatelia Swinhoe, 1907...

 typically have microbasic b-mastigophors and microbasic amastigophors, though the latter are not always present in adults.

Genera

The following three genera are recognised by the World Register of Marine Species (WoRMS):

• Isometridium
• Metridium
  Metridium
  Members of the genus Metridium, also known as plumose anemones, are sea anemones found mostly in the cooler waters of the northern Pacific and Atlantic oceans. They are characterized by their numerous threadlike tentacles extending from atop a smooth cylindrical column, and can vary from a few...
  
  - de Blainville
  Henri Marie Ducrotay de Blainville
  Henri Marie Ducrotay de Blainville was a French zoologist and anatomist.Blainville was born at Arques, near Dieppe. In about 1796 he went to Paris to study painting, but he ultimately devoted himself to natural history, and attracted the attention of Georges Cuvier, for whom he occasionally...
  
  , 1824
• Paraisometridium

Of these genera, Metridium is the most speciose while Isometridium and Paraisometridium are monotypic taxa.