Pistillate scales ovate, as long as or much shorter than the perigynia, margins narrowly or broadly hyaline. Perigynia 2-4 × 1.5-1.8 mm, distal margins smooth; beak smooth or sparingly serrulate. 2n = 50. Fruiting Jul-Aug. Mires and heaths of the boreal forest with disjunct occurrences southward in the alpine zone of eastern and western mountain ranges, primarily on calcareous substrates; 20-3400 m; Greenland; Alta., B.C., Man., Nfld. and Labr., N.W.T., Nunavut, Ont., Que., Sask., Yukon; Alaska, Calif., Colo., Mont., Nev., N.H., Wyo.; Mexico; South America; Eurasia. A. Cronquist (1969) placed Carex capitata in Utah; the species is not listed by B. J. Albee et al. (1988), nor have specimens been seen from there. Carex capitata and C. arctogena differ in habitat (boreal mires versus alpine heaths), habit (mat-forming versus tufted), and morphology of the pistillate scales (much shorter and narrower than perigynia and with narrow hyaline margins versus as long as perigynia and with broad hyaline margins) and perigynia (beak gradually formed and smooth versus beak and may be sparingly serrulate).