Disc flat with short, vertical peripheral skirt. Jelly thin, in life disc flexing from flat, through hemispherical to fully spherical (with opposite sides of margin meeting) in overall shape; the skirt supported by strong ribs with equal intervening gaps; one extra-circular radial canal and one marginal tentacle per rib; 1-2 lappets and ribs between adjacent rhopalial lappets (? depending on stage of growth). Exumbrellar rhopalial pits somewhat conspicuous, situated near upper margin of skirt, rhopalium short, stubby. Rhopalial lappets long, pointed, straight-sided, without gap between; tentacular lappets shorter, but arising from position of end of thick ridge-like extension of mesoglea so terminating at same level as rhopalial lappets, similarly pointed. Marginal tentacles ca. 24, alternating in ones and twos with the 16 rhopalial lappets (with some inconsistencies in sequence in most individuals), easily lost through damage. Marginal tentacles fine, in life approx. same length as disc diameter, arising from exumbrella surface 1/5 of distance between margin and ring canal. Mouth-arms 8, arranged in pairs, tapering gradually to blunt point; length in life approx. 1/2 bell diameter; fused sub-basally for short length, basal spaces between forming 8 heart-shaped genital ostia. Stomach circular, occupying central 1/3 of disc. Radial canals ca. 48 (depending on stage of growth), wide, slightly sinuous, irregular, leading to wide peripheral ring canal. The 16 per-, inter- and adradial canals continuing beyond ring canal for short distance then forking on either side of each rhopalium; between two rhopalial radii 1-2 radial canals extending into tentacular lappets. Gonads 8 (abnormal numbers recorded), arranged in (near) continuous ring around periphery of stomach, diameter of gonad ring approximately 1/3 of disc diameter.
Ground-color of epidermis of disc pale orange-translucent, radial canals whitish, mouth-arms pale lilac, marginal tentacles colorless. Red pigment granules reported throughout mesoglea.
(Partly after Bigelow, 1909; Russell, 1962; Larson, 1986).