Body elongate, up to 300 mm in length; coloured red or brown, the ventral side is lighter.
There are usually 12 tentacles, with 2 pairs of lateral digits. The outer digits are the largest; the terminal digit is rudimentary or absent. The inside of the tentacles bears 2 longitudinal series of small round sensory organs (L. digitata tentacles).
Tube-feet are absent.
The calcareous deposits in the skin consist of anchors and anchor plates. The anchors about 0.3-0.35 mm long, with much diverging and serrate arms. Sometimes there are very large anchors, lying in a row in each dorso-lateral interradius; their arms are smooth and are much less diverging than in the smaller anchors. The anchor plates are more or less regular, racquet-shaped, with a narrow handle and usually 4 larger, central holes; the holes are smooth and are smaller in the anterior end of the body (L. digitata spicules).
This species lives in muddy-sandy bottoms, from lower shore down to about 70 m.
In the North Sea this species is known from the Shetland Islands. Elsewhere it is distributed on the British and French Atlantic coasts and the Mediterranean.