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.