Body strong, cylindrical with up to 300 segments.
Prostomium bluntly conical, about as long as broad. First segment somewhat longer than second one. Parapodia with short, broadly rounded prechaetal lamellae and somewhat longer postchaetal lamellae. Aciculae black with light tips, often a light acicula in between the dark ones. Anterior 50-80 chaetigers with winged capillary chaetae. Hooded hooks start at chaetiger 1-9 (seldom at 25-55); anterior ones slender and with 5-7 similar distal teeth, posterior ones thicker and with one big and 4-5 smaller distal teeth (L. magnidentata-detail). Mandibles X-shaped, fused for over half their length, with straight edges. Maxillae I: hooked forceps; maxillae II: with four teeth; maxillae III: bidentate and maxillae IV: unidentate. Maxillary carrier hardly longer than broad, laterally incised.
Up to 340 mm for numerous segments.
In alcohol pale yellow or brown, often with transverse banding on anterior segments.
Northern North Sea to Skagerrak.