Body elongate, up to 50 mm in length and about 1.5-3 mm thick; coloured whitish.
There are 10 tentacles, each with 2-4 pairs of digits. The unpaired terminal digit is the longest (L. decaria tentacles).
This species lacks tube-feet.
The skin contains calcareous deposits which consist of serrate anchors and smooth anchor plates. The anchors are usually narrower than the anchor plates.
There are 6 serrate holes around the central hole in the anchor plate (L. decaria spicules).
This species has been recorded from depths of 40-70 m.
This species is known from the Trondheim Fjord to the Kattegat.