Haliactiidae usually with rounded aboral end. Column not divisible into regions, smooth. No sphincter. Tentacles rather numerous, short, the inner longer than the outer ones. Two weak siphonoglyphs and two pairs of directives. 6 pairs of perfect, filamented mesenteries with strong restricted retractors, imperfect mesenteries in cycles, without retractors and as a rule without filaments and gonads; but the mesenteries of the second cycle may have filaments and gonads in their uppermost part. Parietal muscles elongate. Acontia present, their nematocysts basitrichs and microbasic amastigophors. Cnidom: spirocysts, basitrichs, microbasic p-mastigophors, microbasic amastigophors.
H. arctica Carlgren 1921
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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