Hermaea bifida

(Montagu, 1815)

The elongated body reaches 20 mm in extended length and is coloured white, with a rosy blush on the rhinophores and elsewhere on the head. The dorso-lateral cerata are arranged in up to fourteen indistinct rows, with a maximal number of three cerata per row on each side of the body. Each ceras is elongated, pointed at the tip and faintly tuberculated. The digestive gland shows through the skin red-brown, fading if unfed. The metapodium is long and slender. The rhinophores are inrolled. The anal opening is antero-dorsal, just behind the head.

This delicate species is usually found on red algae such as Griffithsia, Delesseria or Heterosiphonia, rarely on the shore, more often in shallow water offshore.

Around the north and west coasts of the British Isles and off Helgoland (Distr. H. bifida). It has also been recorded from the Atlantic and Mediterranean coasts of France.