Simple or gregarious Corallimorpharia. Longitudinal muscles in the ectoderm of the column present or absent. Tentacles simple, always provided with acrospheres which may be well developed or weak. More than one tentacle is connected with at least the older endocoels. Endocoelic tentacles in each row variable in number. Spirocysts always present, usually very numerous.
Definitions and contained taxa are those of Oscar Carlgren as published in 1949 : Kungl Svenska Vetenskapsakadamiens Handlingar, Series 4, Volume 1, Number 1