Haloclavidae with smooth body, not divisible into regions and with round, proximal end. Sphincter fairly well developed, endodermal diffuse. Tentacles 20 (10+10) the inner (endocoelic) considerably smaller than the outer (exocoelic) ones. Longitudinal muscles of tentacles and radial muscles of oral disc ectodermal. A single, deep, ventral siphonoglyph. Mesenteries 10 pairs, only 8 of which are perfect and fertile arranged as the macrocnemes in Edwardsia, the ventrolateral mesenteries of the second cycle absent. Retractors of mesenteries diffuse, fairly weak. Cnidom: spirocysts, basitrichs and probably microbasic p-mastigophors.
O. diomedeae Mc Murrich [sic] 1893
Definitions and contained taxa are those of Oscar Carlgren as published in 1949 : Kungl Svenska Vetenskapsakadamiens Handlingar, Series 4, Volume 1, Number 1