(Verrill, 1870)
Description:
Specimens up to 5 mm. Dorsal surface round to oval, covering the entire head, body and foot. Colour yellowish or yellowish green with black spots, entirely black or dark brown. Rhinophores with wings, placed in the front part of the body. The foot is flat and nearly round. The head bears two short oral tentacles. Genial aperture is on the right side of the body, just behind the head. The penis is unarmed. Anus is in the hind end between foot and dorsum in the midline of the body. A series of gill leaflets are present on both sides of the anus. Two to four branchial glands are present on each side at the bases of the gills.
Habitat:
From just above low water level to a depth of 5 m in brackish habitats (6.7 - 32,1 รค). Found on the holdfasts of Fucus serratus , on leaves of Zostera marina , and between Tubularia sp.
Distribution:
The species is centred along the Atlantic coast of the USA. Isolated populations have been found in Brazil, The Netherlands (Zuiderzee), France and in the Black Sea. European settlements and those in Brazil probably originate from animals transported by ships (Distr. C. obscura).