Andreaea rupestris Hedw., Spec. Musc. Frond. 47. 1801.
Plants blackish green to black, or reddish brown to dark brown, up to 2 cm high in dense tufts. Stems erect or ascending, simple or sparsely branched. Leaves 0.70–0.76 mm × 0.30–0.36 mm, imbricate, appressed when dry, lanceolate from an ovate base to ovate-panduriform to panduriform, with acute to obtuse apex; margins entire, sometimes crenulate above in reference to the mammillae present on laminal cells, slightly incurved; upper laminal cells irregularly quadrate, rounded-rhomboid to short-rectangular, 8–16 µm × 4–8 µm, irregularly thick-walled, papillose to nearly smooth; basal cells elongate to narrowly rectangular, 20–60 µm × 2–6 µm, with strongly and irregularly thickened walls, pitted. Autoicous or dioicous. Perichaetial leaves oblong-lingulate, obtuse to acuminate, about 1.5–2.0 mm long. Pseudopodium 1.5–2.0 mm long. Capsules exserted, ovate-oblong, blackish brown, split to 4 values from near the base to the apex when mature. Spores red-brown, 20–28 µm in diameter, densely papillose.
Syntypes. Sweden: "Bructeri," sin. coll.; England, "Annaemontani," sin. coll.
Andreaea petrophila Ehrh. ex Fuernr, Flora 10 (Beibl. 2): 30. 1827.
Andreaea rupestris is characterized by the following features: (1) shortly lanceolate leaves with a rather blunt apex and an ovate to panduriform base; (2) capsule dehiscence from near the base to the tip when fully mature; and (3) basal laminal cells elongate to narrowly rectangular.