Atti Accad. Sci. Siena 9: 231, plate 1. 1808.
Leaves 0.4–0.8 mm; margins ciliate-dentate, teeth often of more than 1 cell; apex acute to long-acuminate; medial laminal cells 30–45 × 9–12 µm.
Phenology: Capsules mature late spring- summer.
Habitat: Rock, bark at base of trees
Elevation: low to high elevations
B.C., Ariz., Calif., Colo., Idaho, Oreg., Wash., Mexico (Baja California Sur), Europe, n Africa.
Fabronia pusilla is easily distinguished by its long-acuminate and ciliate-dentate leaves.