Actiniaria with well-developed pedal disc but without basilar muscles. Column without vesicles and verrucae, nearly always with spirocysts. Margin tentaculate. No sphincter. Tentacles in variable number, often with their aboral side thickened, either in two alternating cycles or, owing to the curious development of the mesenteries, arranged in a way very different from the normal type, but usually in cycles. Longitudinal muscles of tentacles and radial muscles of oral disc ectodermal, with a slight mesogloeal tendency. Oral disc sometimes lobed. One siphonoglyph or two. Usually more mesenteries than the directives attached to the siphonoglyph. Arrangement of the mesenteries curious. After the first 12 mesenteries (six couples) are developed, all subsequent pairs appear in the lateral endocoels and have their longitudinal muscles oriented as in the directives. Cnidom: spirocysts, basitrichs, microbasic p-mastigophors.
Definitions and contained taxa are those of Oscar Carlgren as published in 1949 : Kungl Svenska Vetenskapsakadamiens Handlingar, Series 4, Volume 1, Number 1