Body long; thorax cylindrical, slightly flattened dorsoventrally; abdomen tapering.
Tentacles numerous, thin, moderately long. Upper lip broad and rounded. Buccal segment ventrally rounded, entire. No eyespots.
One pair of arborescent gills on segment 2. Stems of gills thick and long with a thick, elongated mass of spirally arranged branches. Right and left gills often unequally developed. Lateral lobes on segments 2-4, those of segment 2 most prominent. Ventral shields on about 15 segments. Notopodial chaetae smooth, alternating in the bundles between short- and long-shafted ones, starting at segment 4. Seventeen thoracic chaetigers. Uncinigerous tori start at segment 5. Uncini in double rows on segment 11 to 20 (P. lornensis-detail).
Pygidium without appendages, smooth.
Up to 49 mm long.
A thin layer of secretion with a thick and relatively firm incrustation of fine particles.
In formaldehyde or alcohol pinkish or yellowish grey.
On mud or mud mixed with sand and clay; 25-94 m.
Norwegian south coast, Swedish west coast, north coast of Jutland, West coast of Scotland.