Gonactiniidae with smooth, cylindrical body. Margin not undulated. Column with well developed longitudinal muscles and nerve-stratum. Tentacles rather long, few, not constricted at their base, not swollen at the apex. Usually 8 mesenteries perfect but in connection with reproduction by transverse fisison [sic] the number of perfect mesenteries may be a little irregular. Imperfect mesenteries 8, four forming pairs with the perfect mesenteries, and four forming two pairs in the dorsolateral exocoels. Only the lateral perfect mesenteries fertile, the perfect mesenteries and sometimes the fifth couple with filaments. Longitudinal muscles of the mesenteries and the parietobasilar muscles weak. Reproduction by transverse fission. Cnidom: see the family. A single species.
Actinia prolifera M. Sars 1835
Definitions and contained taxa are those of Oscar Carlgren as published in 1949 : Kungl Svenska Vetenskapsakadamiens Handlingar, Series 4, Volume 1, Number 1