Column cylindrical, with conspicuous mesogloeal tubercles arranged regularly in longitudinal rows; tentacles arranged in four or five cycles, with an apical orifice, aboral side of tentacles often thickened at the base; sphincter weak, mesogloeal, thus tentacles can not be completely retracted; longitudinal musculature of tentacles mesogloeal; mesenteries arranged according to Actinostola-rule; oldest cycles of mesenteries sterile.