Polytrichum laevigatum Wahlenberg, Fl. Lapp. 349, fig. 22. 1812; Psilopilum arcticum Bridel; Oligotrichum glabratum (Hooker) Lindberg; O. laevigatum (Wahlenberg) Bruch & Schimper

Stems 7-10(-18) mm, slender, rather wiry. Leaves 1.5-1.8(-2.5) mm, ovate to oblong-obovate, erect-incurved when dry, only weakly spreading when moist, rounded concave in lamellate portion, becoming abruptly cucullate approaching the obtuse apex; margins irregularly dentate with projecting ends of obliquely oriented, rhomboidal marginal cells, usually hyaline-margined; costa ending in or just below apex, smooth on the back above, rarely with a few low, adaxial lamellae; lamellae 8-15, 6-12 cells high, margins deeply incised, coarsely and irregularly dentate; cells of leaf base short-rectangular, narrower at margins; median cells of lamina 12-24(-30) µm wide, thin- to firm-walled; perichaetial leaves 3.8-4.5 mm, erect, twice as long as stem leaves or longer. Seta brown, 7-15 mm. Capsule 2.6-4 mm, greenish to dark brown to blackish brown, variable in shape, asymmetrically ovoid and gibbous; peristome teeth 200-320 µm.

Habitat similar to that of Psilopilum cavifolium, somewhat rare and local in arctic North America; Nfld. and Labr. (Labr.), Nunavut, Yukon; Alaska; arctic and subarctic Eurasia (southward to 61ºN, including Archangelsk Province, e Siberia, Altai); Atlantic Islands (Iceland).

In Nunavut, Psilopilum laevigatum is known from Baffin Island.