Body thin, long and thread-like. Borders of segments difficult to recognize. Each segment with tufts of sensory cilia in posterior half, and three pairs of adhesive organs: a ventral, dorsal and lateral pair, the latter formed by a group of 6-10 glands, sometimes more. Pygidial lobes not wider than posterior part of trunk, simply rounded with paired subterminal groups of ventral adhesive glands. Bacillary glands and other epidermal glands present.
Segments 6-9 are fertile. Females never with more than two oocytes per segment at a time. Males with one pair of spermioducts in each fertile segment.
Up to 4 mm for about 15 segments.
Transparent, with striking, refringent, greenish yellow epidermal glands, more or less irregularly distributed in the entire epidermis and concentrated in two bands on both sides of ventral ciliated groove.
Relatively clean sandy sediments of medium grain size; surface layers of intertidal sand flats.
North Sea (Sylt, Amrum, Helgoland Dune, Dutch and Belgian coast, east coast of England), English Channel (Ambleteuse, Roscoff area), Irish Sea (Northern Ireland, North Wales).