Plants in cushions or low, sometimes extensive tufts, olivaceous or yellowish brown. Stems 0.8-2.5 cm, central strand distinct. Leaves erect or curved, rarely falcate, imbricate when dry, lanceolate to ovate-lanceolate, strongly keeled distally, (0.9-)1.4-2(-2.3) mm, 1-stratose; margins usually recurved to just before the apex, proximally often more broadly recurved on one side of leaf, distal ¹/3 often plane, smooth, 1-stratose with 2-stratose sections; apices acute or sub-obtuse; costa excurrent as a denticulate, flexuose, usually strongly decurrent awn, often embracing part of the lamina, smooth; basal marginal cells short-rectangular, occasionally with transverse walls thicker than longitudinal walls; distal cells mainly short-rectangular or quadrate, 7-10(-11.5) µm wide, smooth, usually strongly sinuose. Sexual condition autoicous. Capsule orange-brown or reddish brown, campanulate, 0.5-0.6 mm; exothecial cells short-elongate or isodiametric, often more or less quadrate, thin-walled or slightly thickened, small trigones usually present; stomata present; operculum rostrate; peristome rudimentary, consisting of basal segments, or absent, yellowish, papillose. Spores 8-12 µm, verruculose.

Capsules mature late spring to early summer. Shallow crevices and cavities on basalt cliffs; low to moderate elevations (60-1200 m); Greenland; N.W.T., Que.; Alaska.

The long, usually strongly decurrent awns and the campanulate capsules absent a distinct peristome separate Schistidium cryptocarpum from other arctic species of the geunus. Mogensen and Blom provided further details on this species. It should be confused only with S. flaccidum, a more southern species, which differs in having a mamillate rostrum and a cupulate capsule.