(Linnaeus, 1758)
Description:
Body slender, cylindrical.
Peristomium without eyes. 18-20 pairs of radioli, with a high membrane. Operculum as in Pomatoceros lamarcki except the ampulla is shallow (dish-shaped) and the distal part often conical, with or without projections (P. triqueter-drawing). Peduncle inserted laterally on the operculum. Collar high, incised laterally, with smooth, curved borders.
7 thoracic segments; thoracic membrane wide. Chaetigers 1 and 2 with capillay chaetae; these disappear in older specimen. Other thorax segments with winged capillaries. Uncini in thorax triangular, with 6-10 strong teeth in a single row; the lowest tooth is tongue-shaped, with an incision at the tip.
Abdomen with sicle-chaetae, with a long tip and small teeth on the concave side. Uncini in abdomen the same as on the thorax (P. triqueter-chaetae).
Pydidium with 2 small round lappets.
Size:
Up to 25 mm for 100 chaetigers.
Tube:
Like that of Pomatoceros lamarcki but always with only a median ridge.
Colour:
Abdomen yellowish greenish, red or brown. Crown with white blue yellow red or brown cross-stripes.
Habitat:
On rocks; mainly sublittoral.
Distribution:
Arctic, eastern North Atlantic up to Mediterranean, Adriatic, Black and Red Sea up to English Channel whole North Sea, Skagerrak, Kattegat, the Belts and Öresund up to Bay of Kiel.
Remarks:
P. triqueter and Pomatoceros lamarcki have been considered to be one species, but are recently regarded as separate species.