Medusae with almost hemispherical umbrella divided by peronial grooves or similar structures so that umbrellar margin is lobed. Four radial canals; no typical circular canal, but solid core of endodermal cells around umbrellar margin. Tentacles solid, inserted on exumbrellar surface well above margin so that tentacular bulbs are not in direct contact with endodermal circular core. Narrow exumbrellar cnidocysts bands may alternate with tentacles. Manubrium simple, elongate, quadrangular or tubular; mouth opening quadrangular to circular. Gonads in four masses on proximal part of manubrium, or as epidermal lining of interradial pockets of manubrium. Marginal sense organs apparently missing. Cnidome: macrobasic mastigophores (Cnidocyst types). Reproduction unknown.