Lineus viridis (Müller, 1774)

Length up to 11 cm, width up to 4 mm. A long and slender, greenish species with somewhat paler lateral margins and distinctly paler ventral side. The typical heteronemertean lateral slits on either side of the head extend back to the region of the brain, which is usually visible through the body wall as two diffuse reddish spots, and at least two eyes are situated along the dorsolateral margin on either side of the head (lacking in young juveniles). Sexually mature individuals have gonopores (visible as whitish spots) arranged in a longitudinal dorsolateral row on either side of the body. Difficult to separate from Lineus ruber and Micrura varicolor.