Tiny, discoid, thick, with finely warted surface and crenate coronal groove. Disc flat, diameter recorded to ca. 15 mm; central region 2.5 wider than high; it and lappets with numerous fine nematocyst warts; coronal groove prominent, crenate, delimiting central half of disc. Marginal lappets 16, with alternating 8 thick tentacles and 8 prominent rhopalia in clefts between; radial grooves running to lappets, separating thick pedalia. Tentacle clefts and rhopalial clefts about equal in depth. Circular muscle narrow, less than 1/3 lappet length in radial extent. Gonads 8, spaced apart, oval to rigidly elongate in outline, (?always) centripetal to circular muscle.
Coloration varied: jelly translucent-milky, greenish or light brownish; gonads (male) bright yellow or (female) brown to red. Pigment patches between gonads reported by Thiel (1966). Small crystalline spots on exumbrella.
(After Mayer, 1910; Larson, 1986).