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.
Rock, bark at base of trees. 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.