Body very long, strong and slimy with numerous segments.
Prostomium is small, roundly conical. Eyes are not discernible.
Peristomium as long as the following segments, without chaetae.
Thorax with 13 chaetigers with broadly winged capillary chaetae only. Thoracic parapodia are rudimentary.
Posterior part of the body with numerous segments with small notopodia. Neuropodia are tori. Abdominal segments with slightly bent hooded hooks only (D. caducus-detail).
Gills in tufts of up to 20 filaments, inserted from 20th segment posteriorly.
Genital hooks absent.
Pygidium is very short, without cirri.
Up to 300 mm and occasionally up to 1 meter, for numerous segments.
Anterior body red or grey-brown, iridescent; posterior body greenish-yellow, Gills red.
In sand and muddy sand. Low water.
Cosmopolitan; North Atlantic up to English Channel, northern North Sea, Skagerrak.