Body elongate, up to 300 mm in length but usually smaller, about 5-9 mm thick; coloured red-pinkish.
There are 12 tentacles with usually 8-9 pairs of short digits, the terminal digit is also short (L. bergensis tentacles).
This species lacks tube-feet.
The skin contains calcareous deposits which consist of anchors and anchor plates, which are conspicuously larger than in L. inhaerens and Leptosynapta decaria and Leptosynapta minuta. The serrated anchor is usually broader than the anchor plate, which may also be partially serrated (L. bergensis spicules).
From shallow water down to about 50 m.
In the North Sea this species is known from Helgoland. Elsewhere it is found on the Scandinavian coasts and the Faeroe Islands.
This species is often regarded as identical with Leptosynapta gallienii (Herpath). The difference in anchor plates would, however, seem to be too great for simply uniting them. According to Mortensen (1927), it is more correct to follow Ostergren in regarding them as separate species.