(Düben & Koren, 1845)
Body thick, ovoid, tapering posteriorly into a long, thin "tail"; usually curved into a U-shape; up to 60 mm in length; coloured yellowish or brownish.
There are 10, tree-shaped tentacles.
The tube-feet are not abundant on the dorsal side and wholly absent in the posteror part of the "tail".
The skin is thick with numerous, closely spaced or even overlapping, calcareous deposits, which consist of large, smooth, often tubercelated, fenestrated plates (T. raphanus spicules).
This species lives burried in sandy or muddy bottoms, with only the tail-end projecting above the surface; from shallow waters down to 1000 m.
In the North Sea this species is known from the Shetlands Islands down to Northumberland on the British east coast. Elsewhere it is distributed from Norway down to the Mediterranean.
Several Thyone species are very similar to this species, but usually they grow much larger and do not possess a long "tail".