Below the oral disc is a swollen collar with up to 60 rings of curved hooks with broad triangular bases.

The surface of the trunk is covered with dome-shaped papillae (fleshy projections from the body wall) of various sizes, each tipped with a dark coloured ring.

It has been recorded in Norway but its main range extends from the British Isles southwards to the Cape Verde Islands and the Mediterranean Sea.

In the British Isles, it is mainly found on the western coast of Ireland as well as in Shetland, Orkney and the Hebrides, and sporadically elsewhere.

It burrows in soft sediments, such as muddy sand and gravel, intertidally and to a depth of about 90 m (300 ft); it conceals itself under rocks and in crevices and is often associated with the red crustose algae Lithothamnion.