Characteristics of the Family (from Kramp 1961)
Rhizostomes with mouth-arms three-winged. A network of anastomosing canals, issuing from the primary ring canal, does not communicate with the gastral cavity except through the radial canals. Subumbrellar muscles annular. Rhopalar pits with radial folds. Subgenital ostia narrowed by papillae.
Without scapulets; with permanent ring canal; with 16 or 32 radial canals not all extending to umbrella margin; with a continuous genital porticus.
With intracircular network of anastomosing canals communicating with the ring canal, but not always with the 16 radial canals; the eight rhopalar canals extending to the umbrella margin, the eight inter-rhopalar only to the ring canal; mouth arms pyramidal.