Body long, anterior part cylindrical, posterior part tapering.
Tentacles numerous, very long, thick. Upper lip low, broad and thick. Many eyespots.
Two series of gills (on segments 2 and 3), each series consisting of a number of free filaments arranged in transverse rows on dorsum. The filaments contract spirally (T. cincinnatus-detail).
No lateral lobes.
Ventral shields on 10-30 segments. Notopodial chaetae smooth, of two types; long straight ones, and short distally curved ones, starting at segment 3, extending through many segments (over 30), thorax and abdomen not discernible. Uncinigerous tori from segment 6, low, in middle part of body long, often with curved rows of uncini, but never in two parallel rows.
Pygidium with minutely scalloped edge.
Up to 200 mm for over 100 segments.
Irregularly curved, often very long. A tough, transparent layer of secretion, often firmly glued to stones or large shells, the free surface encrusted with coarse sand grains and shell fragments.
In life body pink, orange or brownish with lighter ventral and lateral areas, gills red, tentacles pale pink, orange or brownish with red spots. In alcohol pale yellow.
On most kinds of substrata, ranging from mud through sand to solid rocks. It is especially common and abundant on coarse sand with shells; eulittoral to a depth of about 4000 m; euhaline, temporarily polyhaline.
Eastern North Atlantic to Cape Verde, Mediterranean, American Atlantic, Caribean, West Greenland, Canadian and Alaskan Arctic, White Sea, Siberian Arctic, Bering Sea, Sea of Okhotsk, Japan, North American Pacific, Antarctic; East Greenland, Svalbard, Barents Sea, Jan Mayen, Iceland, Norwegian Sea, the Faeroes, Shetland, Orkneys, North Sea, entire Norwegian coast, Swedish west coast, Skagerrak, Kattegat, the Öresund and the Belts.