This sea anemone has a wide and firmly adherent base. The column is smooth, divided into scapus and capitulum, with a prominent parapet and fosse. The tentacles are slender, short or moderate and very numerous in large or medium sized specimens. Acontia
are present but not readily emitted. Colour is usually white or orange, occasionally buff, yellow or reddish, sometimes bi-coloured. Tentacles usually with a white band near the base. Size up to 120mm across base and 300mm tall but many small forms (dwarf races) occur which rarely exceed 30-40mm across the base. The familiar large 'plumose' form is easily recognised and well known. Smaller varieties may cause difficulty but providing the key characters are considered, no real problem in identification should arise. Reproduces by basal lacerations. Small specimens are frequently mis-identified as Sagartia
spp. but this genus lacks a parapet and bears suckers on the column. Diadumene cincta
and Haliplanella lineata
possess a parapet and lack suckers but are easily distinguished by other features (see relevant descriptions).