Carapace suboval and broader than long, dorsal surface relatively flat and smooth, median and sub-median lobes equally developed and subacute to rounded, sub-medians often slightly in advance of median; outer ventral margin of orbit with a narrow incision. Antero-lateral margins of carapace with first and second teeth usually slightly obtuse, third to fifth spinose, fourth at the most as long as the third. Chelipeds equal in size and stout, carpal process acute and broad, propodus with longitudinal carinae; second to fourth pereiopods moderately thin, ventral margin of propodus with one longitudinal carina extending length of margin (setose on second pereiopod), dactylus styliform, of fifth pereiopod broadly lanceolate, width not exceeding half the length, sometimes with a faint median carina; merus of fifth pereiopod not extending beyond proximal half of merus of fourth.
Carapace length up to 13.5 (35) mm.
Depth range from ower shore to about 84 metres on gravel. Ovigerous May-July, larvae spring-October.
Carapace varying from variegated light brown to dark brown with white reticulations, pereiopods paler, dactylus of fifth tinged with blue.
Orkney, Moray Firth, Aberdeen, Firth of Forth, Northumberland, Yorkshire, Wash, Thames, East Channel, Wight, Channel Isles, Portland, Plymouth, Scilly Isles, Bristol Channel, Isle of Man, Clyde & Argyll, Lewis, Galway Bay, Fastnet, Cork.