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.
Up to 25 mm for 100 chaetigers.
Like that of Pomatoceros lamarcki but always with only a median ridge.
Abdomen yellowish greenish, red or brown. Crown with white blue yellow red or brown cross-stripes.
On rocks; mainly sublittoral.
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.
P. triqueter and Pomatoceros lamarcki have been considered to be one species, but are recently regarded as separate species.