(Linné, 1766)
Diameter up to ca. 30 cm; exumbrella smooth; tentacles 24 in adult, 3 of uniform size per octant, all arising from edge of disc in cleft between lappets. Clefts between tentacular lappets uniform in depth; length of oral arms up to ca. 5 times bell diameter, narrow, V-shaped in section, edges frilled, extreme terminal region (may be lost) spirally coiled. Radial septa (as seen in optical horizontal section) typically narrow, becoming wider centripetally only gradually, inner end roughly truncate.
Coloration greatly varied, but lappets typically brown; rest of bell colorless, or variously colored, or with varied pattern of radiating lines or patches, some lines meeting near-centrally to form isosceles triangles, some specimens having the "triangles" filled in. Ground color varied from colorless through white to yellow, orange and brown, radial lines varied from red through orange to chocolate. Mouth-arms white, yellowish to orange, perhaps also brown.
Sting harmless to severe, possibly environmentally dependent (P.F.S. Cornelius, pers. obs., U.K.).