(Bate & Westwood, 1868)
Mature female more or less asymmetrically pyriform; with distinct segments on the pereion and pleon. The maxillipede has a single very long process on the postero-lateral border, and the posterior process of oostegite 1 is pointed and not incurved. Pereional lateral plates present but often small; not contiguous. Sides of the pleon segments prominent and rounded; five pairs of pleopods, which are biramous and lanceolate; pleopods smooth (not tuberculate) and not projecting laterally when seen from above. Uropodal segment very small, uropods lanceolate. Oostegites completely enclosing the brood chamber. Males with the pleon of unfused segments.
Females about 5 mm long, males 1.8 mm.
Parasitic in the branchial cavity of the hermit crabs Pagurus bernhardus and Pagurus pubescens .
Records from northern and western Scotland, Isle of Man, Devon and Ireland.