Grimmia occidentalis Lawton, Bull. Torrey Bot. Club 94: 461, figs. 1-15. 1967

Plants in open to occasionally compact tufts or mats, olivaceous, often (red-)brown or nearly black. Stems 1-6 cm, sometimes denuded of leaves at base, central strand absent. Leaves usually curved to falcate, sometimes falcate-secund or erect when dry, linear-lanceolate to ovate-lanceolate, concave proximally, weakly keeled or concave distally, 1.4-4(-6) mm, 1-stratose with a few 2-stratose striae or patches distally; margins plane or somewhat erect, rarely weakly recurved, smooth, 2-stratose; apices rounded or acute, usually ending in a fleshy, multistratose apiculus; costa percurrent, rarely short-excurrent, smooth; basal marginal cells quadrate or short-rectangular; distal cells quadrate or rounded, often angular, 6-11 µm wide, smooth, sometimes weakly bulging-mammillose, weakly sinuose. Sexual condition autoicous. Capsule reddish brown, ovoid, cupulate, or short-cylindric, 1.3-2 mm; exothecial cells mostly short-elongate or isodiametric, usually irregularly angular, usually thin-walled, sometimes trigonous; rim darker colored than capsule wall, often red; stomata absent; peristome patent, 350-550 µm, red or orange-red, finely papillose, entire or perforated. Spores 9-12 µm, smooth.

Capsules mature late spring to early summer. Wet or dry rocks, often along intermittent watercourses; high elevations (2000-3500 m); Calif., Colo., Idaho, Mont., Oreg., Nev., Utah, Wash., Wyo.

See comments under 6. Schistidium cinclidodonteum.