Fully grown female markedly asymmetrical. Cephalon small and withdrawn into the pereion in which the segments may be distinct only in the middle region, if at all. Pereion with seven pairs of pereiopods and five pairs of oostegites; the oostegites very large with the anterior pairs elaborately folded and projecting beyond the cephalon. Pleotelson narrowing abruptly, with only four distinct segments, bearing four pairs of stalked biramous pleopods with each ramus round and flat. Uropods barely visible, as two very small tubercles on the club-like posterior part of the pleon. Male pleotelson without segments.
Females up to 11 mm body length, males 4 mm.
It occurs intertidally on Pagurus bernhardus , and in deeper waters on Anapagurus laevis , usually attached to the abdomen but occasionally in the gill chamber.
The species appears to be distributed around all coasts of the British Isles and Ireland.