Plants loosely cespitose, in small clumps; rhizomes short. Culms erect, slender, 10-15(-30) cm, rough distally. Leaves: sheaths pale brown abaxially, persisting, inner band thin, hyaline, sometimes red tinged, truncate or shallowly concave at summit; ligules shorter than wide; blades pale green to gray-green, flat or slightly involute, 5-10 cm × 1-2 mm, shorter than culms. Inflorescences 0.7-1.5 cm × 4-7 mm; proximal bracts scalelike, occasionally bristlelike, shorter than spikes. Spikes 2-3(-4), lateral spikes gynecandrous, closely approximate or the proximal slightly separate, individually distinct, containing 3-8 perigynia, oblong-clavate, 3-6 × 3-5 mm; terminal spike not clavate. Pistillate scales red-brown with lighter center and broad white-hyaline margins oblong-ovate, subequal to perigynia, apex obtuse. Perigynia appressed-ascending, green-white proximally, pale brown distally, often brown in age, finely several-veined, elliptic, 2-3 × 1.25-1.5 mm, widest near middle, apex conic with weakly convex, usually entire margin, subcoriaceous; beak indistinct. Achenes red-brown, broadly obovate, 1.25-1.5 × 1 mm, dull to slightly glossy. 2n = 62, 64.

Fruiting Jul-Aug. Boggy tundra, gravelly shores; 0-200 m; Greenland; Man., Nfld. and Labr., N.W.T., Nunavut, Que., Yukon; Alaska; Europe (Spitsbergen Island, Norway; Vajgac Island, Russia).

Plants from Greenland and Europe often with two spikes and short-beaked perigynia have been called Carex marina subsp. pseudolagopina (Sörensen) Böcher; subsp. marina from North America and Siberia differs in having usually (2-)3(-4) spikes usually equal in size (the terminal spike not larger than the others), narrower leaves, and a more distinct beak. Both types occur in the North American material, subsp. pseudolagopina tends to be more arctic in distribution. The subspecies are not recognized here as separate taxa.