Thenaria (Acontiaria) whose acontia carry only basitrichs. Mesenteries divisible into macro- and microcnemes. Sphincter mesogloeal. Body usually elongate. Macrocnemes with more or less restricted to circumscribed retractors.
Definitions and contained taxa are those of Oscar Carlgren as published in 1949 : Kungl Svenska Vetenskapsakadamiens Handlingar, Series 4, Volume 1, Number 1