Medium-sized to very large Thalassianthidae with well developed pedal disc. Upper part of column with verrucae. Sphincter very weak, restricted to circumscribed. Oral disc more or less strongly folded. Endocoelic tentacles short, branched all round in their upper parts, radially arranged on the greater part of the oral disc, and on the oral sides of short, permanent, cyclically arranged lobes. On the aboral sides of the lobes are bunches of grape-like nematospheres. Exocoelic tentacles orally-aborally flattened, branched at the margin. Longitudinal muscles of tentacles and radial muscles of oral disc ectodermal. 2 well developed siphonoglyphs and two pairs of directives. Numerous pairs of mesenteries, at least 3 cycles perfect. More mesenteries distally than proximally. Retractors well developed, diffuse, band-like. Parietobasilar muscles weak, basilar muscles well developed. All stronger mesenteries, apart from the directives, fertile. Cnidom: spirocysts, basitrichs, microbasic p-mastigophors.
H. Hemprichii [sic] Ehrenberg 1834
?H. hypnoides Saville Kent 1893
H. sp.? Kwietniewski 1896
Definitions and contained taxa are those of Oscar Carlgren as published in 1949 : Kungl Svenska Vetenskapsakadamiens Handlingar, Series 4, Volume 1, Number 1
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