Sideractiidae the elongate column and actinopharynx of which are provided with weak ectodermal muscles extending into the pedal disc, the former with spirocysts. Tentacles arranged in cycles hexamerously at least to the stage with 24 tentacles. They are conical, fairly long, the inner considerably longer than the outer ones. Apex of tentacles forming an acrosphere with large nematocysts, peduncle of tentacle with small papilliform elevations which occur, though in smaller numbers on the oral disc and on the distal part of the column. Oral disc conical. Actinopharynx longitudinally sulcated, without differentiated siphonoglyphs. 6 pairs of perfect and fertile mesenteries. 2 pairs of directives. Variable number of weak mesenteries, sterile and without filaments. Parietobasilar muscles weak. Cnidom: spirocysts, atrichs, holotrichs, microbasic b- and p-mastigophors.
S. glacialis Danielssen 1890
Definitions and contained taxa are those of Oscar Carlgren as published in 1949 : Kungl Svenska Vetenskapsakadamiens Handlingar, Series 4, Volume 1, Number 1