Bythotiaridae Maas, 1905

Bythotiaridae Bouillon et al., 2006: 178; Schuchert, 2009: 442. Bythotiaridi Mayer, 1910: 183.

Diagnosis. Medusae without apical projection, marginal bulbs very indistinct or absent; four, eight or more hollow marginal tentacles, each terminating in a large swelling covered by nematocysts, basal portion of tentacles usually adnate to exumbella; with or without rudimentary or dwarf solid tentacles; four or eight radial canals, simple or branching, with or without centripetal canals growing from circular canal towards centre; with or without gastric peduncle; mouth with four simple or crenulated lips; gonads on manubrium wall, simple or horizontally folded, adradial or interradial; rarely abaxial ocelli on tentacle bases.

Remarks. Bouillon et al. (2006) provided more details and a key to all genera. The subdivision of the family in genera is not well resolved and progress is hampered by the fact that many polyp stages of this family remain unknown. The distinction between Protiaropsis anonyma Maas, 1905 and Bythotiara depressa Naumov, 1960 is clarified. The family name Bythotiaridae Maas, 1905 has priority over Calycopsidae Hartlaub, 1913 (Brinckmann-Voss & Arai, 1998) .