Actiniaria with a rounded or flat base with or without basilar muscles. Column smooth or with outgrowths of one sort or another, rarely (and then especially in the uppermost part) provided with ectodermal muscles. Sphincter absent or present, endodermal or mesogloeal. Tentacles simple or complex, commonly arranged in cycles, sometimes in radial rows. Siphonoglyphs usually attached to directives, rarely to non-directives, when directives are absent. Mesenteries as a rule arranged in cycles, commonly hexamerously. Secondary mesenteries always develop in exocoels. The pairs of non-directives consist of two mesenteries whose retractors face one another, rarely unpaired mesenteries occur. Mesenterial filaments always with ciliated tracts. Holotrichous nematocysts only exceptionally present, and never in the endoderm.
Definitions and contained taxa are those of Oscar Carlgren as published in 1949 : Kungl Svenska Vetenskapsakadamiens Handlingar, Series 4, Volume 1, Number 1
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