Ditrupa arietina

(O.F. Müller, 1776)

Description:
Body long and cylindrical, tapering gradually to the posterior end.
10-12 pairs of radioli, connected at the base by a membrane.
Operculum is a membranous cup or funnel with a rather flat lens-shaped plate with concentric lines.
Peristomium without eyes, the next segment without collar chaetae.
Thorax with 6 chaetigers. Thoracic notopodial chaetae are capillaries and slightly bent, winged chaetae. Neuropodia bear uncini with 16-22 teeth in a single row.
Abdominal uncini are like those on thorax. Capillary chaetae are present on the most posterior 30-25 segments. They are long, thin capillary chaetae.
Between thorax and abdomen two segments without chaetae.
No Apomatus-chaetae.
Pygidium with 2 round, small papillae.

Size:
Up to 20 mm long for 60 segments.

Tube:
Characteristic in being tusk-shaped, not adhered to substratum, made of two layers, the outer thick and vitreous, the inner thin and opaque.

Colour:
Abdomen reddish, crown with reddish cross bands.

Habitat:
Lives unattached to substrata (sand or mud); sublittoral.

Distribution:
Probably world-wide, English Channel, northern North Sea, Skagerrak, Kattegat and northern Öresund.

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