Rostrum straight, with convex upper margin and apex straight or slightly uptumed; about 1.5 x length of antennular peduncle; dorsal rostral teeth variable in number and extending almost to posterior border of carapace, making an angle of about 45 ° with posterior carapace border. Dorsal teeth occasionally serrate in large specimens. Apex of rostrum two points with arcuate space or series of smaller teeth between, ventral border deeply convex. Inner basal part of eyestalk with tubercle.
Carapace with two supra-orbital spines, and antennal, branchiostegal and pterygostomian spines.
Stylocerite acutely pointed, equal to or slightly longer than antennular peduncle.
Scaphocerite outer margin straight or very slightly convex, apical spine exceeding lamellar portion. Third maxilliped equal in length to scaphocerite or slightly longer in large specimens; epipod and exopod present.
Mandible with molar and incisor process, and two-segmented palp.
Pereiopods 1-3 with epipods, pereiopod 4 with reduced setobranch. Carpus of pereiopod 2 seven-segmented. Dactyli of pereiopods 3-5 stout, about 0.25 x length of propus. Pleonite 3 produced dorsally into a very distinct "hook" over pleonite 4. Ventro-posterior of pleonite 4 with robust tooth.
Telson with three to five pairs of lateral spines.
This species exhibits considerable variation in rostral shape which were also figured by Dons (1915). Greve (1963) noted sexually dimorphic characters in rostral shape.
Length up to 60 mm.
Normally mottled dark red, brownish or light green. Sometimes bright red.
Down to about 16-400 metres. Hyperbenthic species, may swim up at night, mostly confined to the nepheloid layer. Off British coasts, ovigerous females have been taken in late January, and off W Norway from February to April. However, off NE Greenland ovigerous females have been taken in September, possibly suggesting a longer breeding period in more northern latitudes.
Distribution in the North Sea:
All North Sea.
A circumpolar species, ranging from Greenland, Spitzbergen, Franz Josef Land and Siberia southwards to W Norway, Sweden and British coasts. Known, in the Westem Atlantic, from Massachusetts northwards and, in the Pactfic, from Alaska and the Bering Sea south to Puget Sound and the Sea of Japan.