Plants robust, in loose tufts, mostly green to yellow, shiny. Stems 1--2(--4) cm. Leaves mostly falcate-secund, lanceolate, gradually subulate, 2--4.5 mm, margins distally 1or 2-stratose; costa 50--60 µm wide at base; distal laminal cells mostly elongate (2--5:1), porose, 7--9 µm wide, smooth or weakly mammillose-roughened; basal laminal cells elongate, porose, alar cells strongly inflated and differentiated. Perichaetial leaves similar to the cauline. Perigonia sessile, located just below perichaetia. Capsule distinctly ribbed when dry, urn 1.3--2 mm. Spores 14--20 µm.

Soil over rock; mostly alpine elevations, occasionally subalpine; Greenland; N.W.T., Nfld., Que., Yukon; Alaska; Europe.

This large species is found in late snow beds and is similar to K. starkei, which is more slender and is commonly found on vertical rock surfaces. A form of K. starkei occasionally occurs in late snow beds, but it has small, erect-spreading dark green leaves; K. falcata also occurs in late snow beds, but can be distinguished in the field by its short, non-grooved capsules.