Plants 0.5--3.5 cm. Stem leaves 2--3 mm, ligulate-lanceolate; margins entire, plane; basal laminal cells firm-walled, clear; distal laminal cells 8--11 µm wide, obscure, densely warty-papillose. Sexual condition autoicous. Perichaetial leaves sheathing, enlarged, erect, short-pointed. Seta 1--1.5 mm. Capsule immersed to half emergent, 0.8--1.3 mm. Operculum short-rostrate. Spores 9--13 µm.

Seasonal wet crevices of neutral to acidic cliffs; 100--2000 m; Greenland; Alta, B.C., N.B., Nfld., N.W.T., N.S., Nun., Ont., Que., Sask., Yukon; Ala, Ariz., Calif., Colo., Conn., Idaho, Maine, Md., Mich., Minn., Mont., Nev., N.H., N.J., N.Y., Oreg., Pa., Vt., Va., Wash., Wis., Wyo.; Europe; Asia.

Amphidium lapponicum differs from the two other North American species by broader leaves and larger, warty, cuticular papillae that obscure the distal leaf cells. It is autoicous and frequently fruiting, in which case the immersed to emergent capsules serve to identify it. Additionally, the larger leaf cells (8--11 µm) differentiate this species from the other entire-margined species, A. mougeotii, which has distal leaf cells smaller (5--9 µm).