(Birula, 1897)
Description
Umbrella with large, globular apical projection [Halitholus yoldiaarrcticae ]. Four undivided radial canals, interradial centripetal canals absent. Gastric peduncle present, base of manubrium attached to subumbrella along arms of perradial cross.
Manubrium almost to velar level, mesenteries absent. Mouth with 4 slightly crenulated lips.
Folded interradial gonads, horseshoe shaped, with diverging folds connected by an interradial, transverse bridge; interradial pits absent. Up to 120 marginal tentacles with basal swellings, no ocelli.
Size
Umbrella up to 16 mm high, 14 mm wide.
Distribution in the North Sea
Kattegat.
World distribution
Arctic, circumpolar; Baltic and Kattegat (glacial relic).