Carapace broader than long, dorsal surface smooth to unaided eye; margin of frontal region concave or with a shallow median incision. Antero-lateral margins of carapace almost straight, particularly posteriorly, forming a noticeable subacute angle with anterior portion of postero-lateral margin. Third maxilliped narrowing anteriorly. Chelipeds equal in size and stout, propodus swollen, margins of merus-dactylus slightly cristate; pereiopods usually smooth. Female broadly rounded bosses on epibranchial-mesobranchial regions usually strongly elevated; chelipeds shorter than in male; abdominal segments 4-6 fused. Male epibranchial-mesobranchial bosses not strongly elevated, sometimes capped with tubercles; chelipeds longer than in female; abdominal segments 3-5 fused; distal portion of first pleopod usually curved and stout.
Carapace length up to 10 (12) mm.
Depth range from 2 to 155 metres, on muddy sand and gravel. Ovigerous in January-August, larvae August-September.
Very variable, carapace from reddish to greyish-white or yellowish-grey, sometimes spotted with red, sometimes with orange margin and pale pink median band. Some specimens variegated brown and black.
Shetland, Aberdeen, Northumberland, Yorkshire, Wash, Thames, Wight, Channel Isles, Plymouth, Scilly Isles, Bristol Channel, Isle of Man, Belfast, Clyde & Argyll, Minch, Mayo, Galway Bay, Fastnet.