Proc. Biol. Soc. Wash. 25: 51. 1912.
Plants loosely cespitose. Culms 20–50 cm, distally scabrous. Leaves 3–5 mm wide. Inflorescences: proximal bracts shorter than or exceeding inflorescences; spikes contiguous or the proximal separate, overlapping, erect, distinct, short-pendunculate, short-oblong or elongate, 8–20 × 5–6 mm; lateral 2–3 (–5) spikes pistillate, of similar length; terminal spike gynecandrous. Pistillate scales dark-brown or black to margins, ovate or broadly lanceolate, shorter than and as broad as perigynia, midvein same color as body, inconspicuous, occasionally raised, prominent, short-mucronate. Perigynia ascending, pale green becoming golden brown, veinless, elliptic, 2.5–3.5 × 1.5–1.75 mm, apex gradually or abruptly beaked, distally papillose; beak 0.3–0.5 mm, entire or shallowly bidentate, smooth. Achenes nearly filling body of perigynia.
Phenology: Fruiting Jun–Aug.
Habitat: Subalpine and alpine meadows, river gravels, shorelines
Elevation: 300–3600 m
Alta., B.C., N.W.T., Yukon, Alaska, Colo., Idaho, Mont., Oreg., Utah, Wash.
The absence of collections of Carex atrosquama in Wyoming is unexpected.