Plants cespitose. Culms obtusely angled, 4-15 cm, glabrous. Leaves: basal sheaths red-brown; sheaths of proximal leaves glabrous, fronts with red-brown spots, veinless, apex U-shaped; blades amphistomic, 1.5-2 mm wide, papillose on both surfaces. Inflorescences: proximal bract longer than inflorescence, 1-1.5 mm wide. Spikes erect, compact; proximal 2-3 spikes pistillate, 1-1.5 cm × 3 mm, base cuneate; terminal spike gynecandrous. Pistillate scales red-brown or black, shorter than perigynia, apex obtuse, awnless. Perigynia ascending, green (becoming white) with red-brown spots on apical 1/2, 3-5-veined on each face, stipitate, tightly enclosing achenes, thin-walled, ellipsoid, 2-2.2 × 1.2-1.5 mm, dull, base truncate, distended, apex obtuse or acute, papillose apically; stipe to 0.3 mm; beak red-brown, 0.2 mm. Achenes not constricted, dull, base adnate to perigynium. 2n = 86.

Fruiting Aug-Sep. Wet sandy or gravelly shores; 0-800 m; Greenland; Man., Nunavut, Que.; Europe (Denmark, Norway, Sweden).

Although placed by K. K. Mackenzie (1931-1933, parts 2-3, pp. 231-231) in sect. Bicolores Tuckerman, Carex rufina is a member of the C. acuta complex, and appears to be very closely related to C. lenticularis. It differs from C. lenticularis in the red-brown spotted perigynia, black scales, and gynecandrous terminal spike.