Thenaria (Acontiaria) whose acontia are provided with basitrichs and microbasic p-mastigophors. No distinct sphincter. Some or all of the inner tentacles typically forming catch-tentacles provided with atrichs and holotrichs; but sometimes apparently these special nematocysts are lacking in individuals of a species which does possess them.
Definitions and contained taxa are those of Oscar Carlgren as published in 1949 : Kungl Svenska Vetenskapsakadamiens Handlingar, Series 4, Volume 1, Number 1