Authors: Roxanne I. Hastings & Dr. Henk C. Greven

Plants in dense cushions, blackish green. Stems 0.5--0.7(--1) cm, central strand weak. Stem leaves ovate lanceolate, 1.5--2 mm, keeled, not plicate, margins plane to incurved distally, awn 0.4--0.8 mm, costal transverse section prominent, terete; distal laminal cells 2-stratose, not bulging, marginal cells 2-stratose, not bulging; medial laminal cells quadrate to rounded, straight, thin-walled; basal juxtacostal laminal cells short-rectangular, straight, thin-walled; basal marginal laminal cells short-rectangular, straight, thick transverse and thin lateral walls, hyaline. Perichaetial leaves not enlarged. Sexuality dioicous. Seta straight, 0.9--1.1 mm. Capsule commonly present, emergent, chestnut brown, ovate with distinct constriction below rim, exothecial cells rectangular, thick-walled, stomates absent, annulus of 1 row, quadrate, thick-walled, operculum conic, peristome absent.

Acidic sedimentary rocks; of conservation concern; 1900--2500 m; Calif.

Grimmia nevadensis is a rare but locally abundant endemic, known only from the Sierra Nevada Mountains of eastern California. Fertile specimens of Grimmia nevadensis can be separated from the closely related G. mariniana by the absence of peristome teeth and by the chestnut brown capsules. Gametophytically, specimens of G. nevadensis contrast with G. mariniana by having a uniform basal areolation of short-rectangular cells with thin lateral walls. If fertile, the immersed, eperistomate capsules will separate G. nevadensis from G. montana and G. alpestris. Sterile specimens can be separated from G. alpestris by the absence of bulging cells, and the uniformly short-rectangular, thin-walled basal laminal cells with a hyaline margin. While both G. nevadensis and G. montana have plane to incurved distal margins and both lack bulging laminal cells, the uniformly short-rectangular, thin-walled basal laminal cells with hyaline margins will identify G. nevadensis. Grimmia nevadensis is easily separated from G. arizonae and G. pilifera. In contrast to both of the latter species, G. nevadensis lacks stomata and peristome teeth, and further its plane to incurved leaf margins differs markedly from the recurved leaf margin of the other two species.