Plants not cespitose. Culms obtusely or acutely angled, 25-130 cm, glabrous. Leaves: basal sheaths red-brown; sheaths of proximal leaves glabrous, fronts lacking spots and veins, apex U-shaped; blades hypostomic, 3-8 mm wide, abaxially papillose. Proximal bract longer than inflorescence, 3-6 mm wide. Spikes usually pendent; staminate 2-3; pistillate 2-4; proximal pistillate spike 1.8-5 cm × 5-7 mm, base obtuse. Pistillate scales red-brown to dark purple-brown, longer than perigynia, apex acuminate, awnless. Perigynia divergent, yellow-brown with pale brown spots on apical 1/2, 5-7-veined on each face, somewhat inflated, loosely enclosing achenes, 2.5-3.5 × 1.6-2.5 mm, leathery, dull, base with stipe to 0.5 mm, apex obtuse or rounded, papillose; beak thickened, 0.1-0.3 mm. Achenes constricted on 1 or both margins, apex rounded; style base straight. 2n = 68, 70, 72.

Fruiting Jul-Aug. Coastal salt marshes, brackish marshes; 0-10 m; Greenland; B.C.; Alaska, Calif., Oreg., Wash.; Europe (Iceland).

Carex lyngbyei is the common sedge of the Pacific coastal salt marshes. It may easily be distinguished from sympatric species by the large, pendent, pedunculate spikes and the leathery, yellow-brown perigynia.

Although the species is also reported to occur in Japan and Korea, some Asian collections show significant morphologic and habitat differences from the North American plants. It is probably most closely related to Carex paleacea and to the South American C. darwinii, and differs from C. paleacea primarily by having acute, rather than awned, scales. Previous reports from eastern North American were misidentifications (J. Cayouette 1987).