Plants in tufts, yellowish green, blackish below. Stems 1.5--3.5 cm, small central strand present. Stem leaves irregularly imbricated when dry, erect when moist, oblong-lanceolate, gradually narrowed into an acuminate chlorophyllose point, 1.5--2.5 × 0.4--0.8 mm, keeled, margins recurved on one or both sides, awns absent to very short, costa projecting on dorsal side; distal laminal cells 1-stratose, in places 2-stratose, margins 1-stratose; medial laminal cells rounded-quadrate, walls slightly sinuose; basal juxtacostal laminal cells rectangular, straight, thin-walled; basal marginal laminal cells quadrate to short-rectangular with thickened transverse walls. Gemmae in clusters, globular, yellowish green to orange, multicellular, on hyaline, deformed leaf apices. Sexual condition dioicous. Seta straight to slightly curved when moist, 3--5 mm. Capsule extremely rare, exserted, brownish, oblong-ovoid, smooth, exothecial cells isodiametric, thick-walled, annulus present, operculum with long straight beak, peristome teeth orange, fully developed, smooth below, perforated and papillose distally. Calyptra mitrate.

Exposed, damp acidic rock in boreal and alpine meadows and slopes; 200--3000 m; Alta., B.C., Nfld., N.S., Ont.; Alaska, Calif., Colo., Idaho, Mont., Mich., Utah, Wash., Wyo.; Eurasia.

Because of the always abundantly present gemmae on leaf apices, Grimmia anomala has often been confused with Grimmia hartmanii. Indeed, Grimmia anomala has frequently been treated as a variety of G. hartmanii (G. N. Jones 1933, E. Lawton 1971). However, as pointed out by O. Vitikainen (1969), the ecological and morphological differences with this latter species are so constant and distinct, that there is no doubt that it can be treated as a separate species. Special features of G. anomala are stems with a central strand, and longitudinal ridges on cell walls in the distal part of the leaf that resemble papillae in cross section. It tends to prefer upland habitats. In contrast, Grimmia hartmanii is principally a lowland species, frequently growing on boulders in forests. It lacks a central strand and longitudinal ridges are absent. Its spreading secund distal leaves taper to long sharply keeled apices.