Prostomium very small, with two eyes, without antennae, ventrally and laterally enclosed by the U-shaped peristomium. Peristomium with two tentacles.
Anterior part of body consists of nine segments bearing only long notopodia with a small fan- or spear-like chaetae. Fourth notopodium with big, distally broadened, concave or toothed hooks. Neuropodia absent.
Middle body region with 5 segments bearing fin-shaped notopodia and neuropodia with uncini.
Posterior region of 20-70 chaetigers with long cylindrical notopodia with embedded chaetae and bilobed neuropodia with uncini.
Pygidium without appendages.
Up to 250 mm for 85 segments.
U-shaped, circular in section, made up of many layers of whitish membrane.
Greenish yellow to off-white. Mature males white, females orange.
On sand and rocks around or below low water.