Prostomium bilobed, weakly incised anteriorly or rounded, caruncle to end chaetiger 3. Up to 2 pairs of eyes. Dark pigmentation along prostomium and on peristomium, sometimes on pygidium. Palps often with black bars. Pigmentation may be absent. No notochaetae on chaetiger 1. Modified spines of chaetiger 5 7 simple hooks with flange on concave edge. Strong hooks on posterior chaetigers. Branchiae begin on chaetiger 7, long & filiform, end before posterior notochaetal hooks begin. Pygidium saucer-shaped.
Up to 40mm for 180 segments and 2mm wide at chaetiger 5.
South Africa: northwest to southeast coast.
English Channel, Atlantic coast of Europe, Australia, New Zealand and the Mediterranean Sea (Type locality Bay of Naples).
Common pest of farmed abalone and oysters, but mainly on latter. Boring stimulates the production of mudblisters. Occurs less often as epifauna on shells.
Brood capsules joined, resemble sausage. Adelphophagic larvae, brooding adults usually present during spring. Females producing planktotrophic larvae recently found.