Head smooth, domed and skull-shaped. Body stout, with varying numbers of small, paired dorsal tubercles on all segments except on 1; tubercles may be elongate in large specimens. Posterior regions of segments 2, 3 and 4 often with a single tubercle behind the pair. Maximum length 13 mm in male and 8 mm in female.
Antenna 1 about two-thirds of the body-length, sparsely covered with short setae, which are not arranged in parallel rows; flagellum of two articles. Mandible without palp.
Propodus of gnathopod 1 with a proximal spine. Gnathopod 2 inserted in the posterior third of the segment, often massive in large males; palm of propodus concave, with a proximal spine and a median tooth. In old and large males and females, segment 2 and gnathopod 2 may be covered in dense, fine setae.
Gills club-shaped, on segments 3 and 4 only.
Pereiopods 3 and 4 absent. Pereiopods 5, 6 and 7 with a pair of grasping spines on the propodus, and two to four accessory spines proximal to the grasping spines. Female gnathopod 2 inserted in the anterior half of the segment; anterior incubatory lamellae setose.
Abdomen with a pair of lobes and a pair of biarticulate appendages in male, in female without either.
Midshore level to sublittoral. Frequent in rock pools and gullies, on algae, hydroids and bryozoans.
Widely distributed in the North Sea, possibly more frequent in north.