Disc up to ca. 1.5 m in diameter, flat, thickest in central region; margin with 8 very wide, deeply cleft tentacular lappets, and 16 narrow, semi-circular rhopalial lappets flanking the rhopalia in pairs; tentacles fine, numerous, roughly circular in cross-section, almost entirely in 8 groups inserted in straight, narrow fields typically 2-5 tentacles in radial extent, the groups extending whole width of each tentacular lappet, but in many specimens also extending onto adjacent region of rhopalial lappet; in some also a few tentacles arising from underside of centre of lappet, the number increasing with age; typically ca. 30-250 tentacles per octant, perhaps more in large specimens. Circular subumbrellar musculature near-circular in alignment, in 16 alternating wide and narrow muscle-fields corresponding to tentacular lappets and pairs of rhopalial lappets; direction of muscle-folds bowed inwards in centre of each field (no radial muscle-fields); mouth-arms comprising four much-folded curtains approximately same width as bell, hanging down in life. Gastrovascular system comprising 16 broad pouches; terminating in narrow branching canals in lappets, with some anastomoses; gonads hanging conspicuously below umbrella.
Coloration much varied, but analysis fraught due to some previous confusion between the two species recognised here. Probably not all variants yet known: apparent color may partly follow recent diet. Ground color of bell variously recorded as pale milk-white to brownish, but many individuals (varied within a local population) are variously strongly marked on exumbrella with 16 broad dark radial lines, extending from near periphery to near centre of bell. Tentacles pale milk-white to brownish. Mouth-arms in individuals with pale bells also pale, milk-white to pale yellow; in those with darker bells, also darker, brownish. Gonads brown.
(Partly after Mianzan, 1986b).