Body oblong oval. Antenna 1 extending beyond article 3 of the peduncle of antenna 2. Antenna 2 flagellum longer than the peduncle and about 1/6 to 1/5 the length of the body. Maxillipedal palp of four articles. Cephalon subquadrate, eyes dorsolateral, prominent. Coxal plates broad, extending over the whole length of the segments 2 or 3 to 7. Pereiopods all more or less alike. Pleon of two complete segments, and one partial suture in the pleotelson. Pleotelson with the sides slightly convex, posterior border emarginate, but there is variation during growth. Uropods usually uniramous.
Males first recognizable from 7-9 mm and ranging to about 30 mm; females from 9-18 mm. Colour of males often uniformly brown, though sometimes with white markings; females generally darker in background colour, often with longitudinal lateral white bands, or alternating white and darker transverse bands.
Generally sublittoral on accumulations of detached algae, but occasionally between tidemarks on attached algae and in large numbers among cast up drift weed. On fully marine coasts.
From Norway to Spain.