Plants 3-8(-13) cm. Stems dark brown. Leaves reddish green, reddish brown, or black when old, spreading, ± flat, not strongly reflexed when moist, broadly elliptic, ovate, obovate, or rarely ± orbicular, (2.5-)3.5-4.5(-6) mm; base short-decurrent, occasionally not decurrent; margins narrowly to broadly recurved or rarely nearly plane, 1-stratose; apex obtuse or rounded, sometimes acuminate or acute, apiculate or cuspidate, apiculus sharp, cusp usually toothed; costa percurrent, excurrent, or rarely subpercurrent; medial laminal cells elongate, (50-)60-75(-100) µm, in diagonal rows, not collenchymatous; marginal cells short-linear or linear, in (2-)3-4 rows. Sexual condition synoicous. Seta yellowish, 4-7 cm. Capsule yellowish, ovate-elliptic, 2-3 mm. Spores 25-70 µm.

Capsules mature summer. Fens, alpine seeps, in shoreline pools; low to moderate elevations; Greenland; Alta., B.C., Man., Nfld. and Labr., N.W.T., Nunavut, Ont., Que., Sask., Yukon; Alaska, Maine, Mich., Minn., Mont., N.Y., Wyo.; South America; Europe; Asia.

Cinclidium stygium is often hidden among other mosses and sedges on wet soils. The species is distinguished by its broadly elliptic, ovate, or obovate leaves often with a sharp, squarrose apiculus or cusp.