Actinodiscidae with weak, diffuse (or no?) sphincter. Marginal tentacles simple, provided with atrichs, discal tentacles mostly branched, sometimes arising from pits on the disc, all without atrichs, arranged at least mostly in radial series. Distribution of the discal tentacles sometimes interrupted by a more or less naked zone separating the outmost, few discal tentacles from the numerous inner ones. (Discal tentacles situated outside the naked zone sometimes not developed?) Mesoglea, when thickened, with rather numerous to numerous cells, sometimes collected into small cell-islets, sometimes containing holotrichs. The animals may live massed together in patches. Individuals rarely with two or more mouths. Cnidom: atrichs, holotrichs, microbasic p- and b-mastigophors. Microbasic p-mastigophors rather short and of typical appearance, not hoplotelic.
Metridium rhodostoma Ehrenberg 1934 [sic]
Actinotryx sancti thomae Duchassaing and Michelotti 1860
R. inchoata Carlgren 1943
R. indosinensis Carlgren 1943
Platyzoanthus mussoides Saville Kent 1893
R. bryoides Haddon and Shackleton 1893
R. howesii Saville Kent 1893
?Phialactis neglecta Fowler 1889
Definitions and contained taxa are those of Oscar Carlgren as published in 1949 : Kungl Svenska Vetenskapsakadamiens Handlingar, Series 4, Volume 1, Number 1