Description: The body is greyish-white and speckled with brown or green pigment. The cerata are few in number and shaped like an urn; this feature distinguishes it from other closely related species. The rhinophoral and oral tentacles have a sub-terminal ring of white pigment and lower down, towards their base, 1 or sometimes 2 bands of brown pigment. Adults may grow to 10mm in length.

Habitat: Reported to feed on shallow water hydroids such as Obelia, Hydrallmania and Laomedea. Often found in large numbers forming mixed populations with Tergipes tergipes feeding on Obelia geniculata on kelp fronds. The spawn consists of lozenge-shaped lumps.

Distribution: Found all around the British Isles, and from the Arctic, Scandinavia and the Mediterranean.

Key Identification Features:

• Cerata few in number, urn-shaped.
• Green pigment patches on body and on cerata.