Carapace with dorsal surface minutely granular, frontal region slightly produced, median lobe advanced, sub-median lobes broadly oval. Antero-lateral margins of carapace with five spinose teeth. Chelipeds usually slightly unequal and stout, carpal process acute to subacute, propodus with longitudinal carinae; second to fourth pereiopods moderately stout, dactylus of fifth styliform but compressed and with setose margins.
Carapace length up to 25 (60) mm.
Depth range; from high shore pools to about 60 metres. Commonest intertidal species, in estuaries. Ovigerous and larvae throughout year.
Variable, carapace from dark green to grey, sometimes with white patches (young specimens), pereiopods brown to greenish-yellow or orange.
Shetland, Orkney, Moray Firth, Aberdeen, Firth of Forth, Northumberland, Yorkshire, Wash, Thames, East Channel, Wight, Portland, Channel Isles, Plymouth, Scilly Isles, North Cornwall, Bristol Channel, Cardigan Bay, Anglesey, Liverpool Bay, Solway, Isle of Man, Dublin, Belfast, Clyde & Argyll, Minch, Lewis, Mayo, Galway Bay, Fastnet, Cork.