(Renier, 1804)
Description:
This species is typically rich reddish-brown or chocolate-brown in colour, sometimes paler on the ventral surface, marked with two slender white or pale yellow longitudinal dorsal stripes, which extend over the full body length, but the background colouration is quite variable. Younger and smaller individuals are often much paler in colour than older animals and may appear almost white. In larger specimens the colour ranges from shades of pink to dark purple. The animals attain a length of 45-50 cm or more. The body is slender and gradually tapers towards the posterior end. The head is bluntly rounded and often rather flattened and spatulate in shape. It does not possess eyes (L. bilineatus-head).
Mclntosh (1873-74) records that though easily maintained in captivity, the species is sluggish in its habits and may remain quiescent for several weeks under a shell or ensheathed in mucus. Proboscis with three muscle layers, but the outer longitudinal layer is reduced to isolated bundles of fibres arranged bilaterally; foregut with longitudinal splanchnic muscles; cephalic glands are moderately well developed.
Habitat:
A lower middle shore to sublittoral species, Lineus bilineatus is found in the British Isles in shelly gravel, muddy sand or clean fine sand, amongst coralline algae in rock pools, under Laminaria holdfasts, beneath stones and boulders, or between mussel or oyster shells.
Distribution:
Geographic distribution extends from Iceland and the Faeroe Islands to Scandinavia, France, the Mediterranean and Madeira. It has also been reported from the west coast of North America (Alaska to California), South Africa and Japan.