Body long and cylindrical with numerous segments.
Prostomium sharply conical, slightly longer than wide. Peristomium a little longer than the following segments.
Parapodium with a short, rounded prechaetal lobe; postchaetal lobe longer, tongue-shaped, becoming slender, cylindrical and erect in middle and posterior segments. Anterior parapodia with winged capillary chaetae and simple multidentate hooded hooks starting on chaetigers 1-5 (L. tetraura-parapodium). Posterior 40-90 segments with simple hooded hooks only. Chaetae and aciculae yellow.
Mandibles Y-shaped. Maxillae I: hooked; maxillae II: 4-5 teeth each; maxillae III: 2 teeth each; maxillae IV: unidentate.
Up to 400 mm for numerous segments.
Light pink or reddish, iridescent.
Found in various kinds of substrata: sand, mud, broken shells, gravel and mixed bottoms, also coralligene, among Zostera and algae, in rock pools, in holdfasts of Laminaria , and in oyster beds from the intertidal zone to abyssal depths.