Rostrum virtually straight, or very slightly downcurved; 1-1.5 x length of antennular peduncle; normally five to seven dorsal teeth (rarely four, eight or nine), two or three of these being behind the posterior edge of the orbit; two to four ventral teeth (rarely one or five).
Carapace somewhat globular in shape, with antennal and pterygostomian spines, plus one supra-orbital spine.
Stylocerite acutely pointed, 0.66-0.75 x length of antennular peduncle, but may be slightly more in very large specimens.
Antennular peduncle with strong, anteriorly-directed spine on lateral border of two proximal segments.
Scaphocerite broad, outer border straight or very slightly concave in large specimens; apical spine not exceeding lamellar portion. Third maxilliped with epipod.
Mandible with molar and incisor process, and two segmented palp.
Pereiopods 1 and 2 with epipods, reduced setobranch on pereiopod 3. Carpus of pereiopod 2 with seven segments. Pleonite 4 with small ventroposterior spine, not apparent in large specimens. Pleonite 6 with strong, acutely pointed posteroventral projection, plus further projection each side of telson insertion.
Telson normally with eight to eleven pairs of lateral spines, but often with different numbers on each side varying from five/four to eleven/twelve; spines not evenly spaced, sometimes occurring in double rows on each lateral border of telson.
Length up to 90 mm, usually 60-70 mm.
Pale with red and yellowish markings on carapace and pleon; tips of chelae brownish black.
Down to about 0-930 metres, normally from 30-300 metres. Hyperbenthic species, may swim up at night, mostly confined to the nepheloid layer. Occurs on various substrata, from hard to muddy. Taken in the Laminaria zone in NE Greenland.
L. polaris appears to have different breeding seasons in different parts of its geographical range: off NW Scotland and N Norway, ovigerous females occur during the summer months, whereas off W Norway in March and May. Off Greenland, ovigerous females have been found throughout the year.
Distribution in the North Sea:
Northern North Sea, Skagerrak.
A circumpolar species, extending southwards to Shetland and the Skagerrak in the Eastern Atlantic, and Chesapeake Bay in the Westem Atlantic. In the Pacific, it extends from the Bering Sea, Okhotsk Sea and the Aleutian Islands south to British Columbia (Canada).