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

Plants in frequently extended mats, blackish green. Stems 1--1.5 mm high, small central strand present. Stem leaves erect with slightly incurved tips when dry, erect-spreading when moist, oblong, broadly rounded and muticous at apex, 1.5--2 × 0.4--0.6 mm, keeled, margins plane to recurved, awns absent, only present in perichaetial leaves, costa weak below, projecting at dorsal side, perichaetial leaves longer and hair-pointed. Distal laminal cells 2-stratose; medial laminal cells rounded-quadrate, ± sinuose, thick-walled; basal juxacostal laminal cells elongate, thin-walled; basal marginal laminal cells cells rectangular, thin-walled. Gemmae absent. Sexual condition autoicous. Seta flexuose to curved, 1--1.5 mm. Capsule usually present, exserted, chestnut brown, oblong-ovoid, wrinkled-plicate when dry, exothecial cells thin to thick-walled, annulus present, operculum conical, peristome teeth yellowish, split and perforated, papillose. Calyptra cucullate.

Dry acidic rock; of conservation concern; 500--1500 m; Ariz., Calif., Nev.; nw Mexico.

Grimmia moxleyi is endemic to the southwestern United States and northwestern Mexico. It is a thermophilous species from acidic rock. In 1999, H. C. Greven found G. moxleyi in California on a vertical, grainy, granite wall in Sequoia National Forest. The plants, with abundant capsules, were growing in a thin mat, covering 3--4 square meters. Grimmia moxleyi is autoicous and usually richly provided with capsules. The species is characterized by growing in flat, easily disintegrating patches with short, keeled, muticous stem leaves that contrast with its much larger awned perichaetial leaves. J. Muñoz (2000) synonymized G. moxleyi with G. orbicularis. Although there are some similarities, G. orbicularis is much larger, it grows in dense cushions on basic rock, setae 2--3 mm, capsules brown, shiny and spherical, operculum mammillate, only the most proximal stem leaves are muticous, and basal juxtacostal cells have thick, sinuose walls.