Genus Orchistoma Haeckel, 1879

Orchistoma Haeckel, 1879: 138;

type species Mesonema pileus Lesson, 1843 (Kramp, 1961) .

Tetracannota Mayer, 1900: 46; type species Tetracannota collapsum Mayer, 1900 by monotypy.

Diagnosis: Medusa with short manubrium on large gastric peduncle; mouth with 8-30 sinuous or crenulated lips; eight or more radial canals, simple, ramified, or in groups of four. Up to 64 marginal tentacles; no marginal cirri, but with thin, filiform, tentaculiform structures devoid of marginal bulbs; gonads usually on proximal parts of radial canals; numerous adaxial ocelli; without statocysts, without cordyli, without excretory pores or papillae.

Hydroid phase unknown.