Plants 0.6--2.5 mm. Stem leaves stiff, erect-appressed when dry, elongate-lanceolate, lanceolate, or narrowly ovate-lanceolate, 2--3.8 mm, acute, bluntly acute, or narrowly obtuse; margins recurved-revolute to near apex, smooth; distal laminal cells 9--14 µm wide, 1-stratose, with 1--3 small, conical papillae; basal laminal cells long-rectangular to rectangular, sometimes slightly nodose. Sexual condition goniautoicous. Seta 1--3 mm. Capsule exserted; urn oblong-cylindric to cylindric, 1.8--2.4 mm, usually 16-ribbed with 8 long ribs extending 1/2--2/3 length of capsule and alternating short 8 ribs; stomates immersed in middle and proximal portion of capsule; peristome usually single; endostome rarely present; exostome teeth 16, rarely united into 8 pairs, finely horizontally-striate below, vertically-striate above. Calyptra oblong-conic, with few to many papillose hairs. Spores 11--15 µm.

Rocks, especially limestone, rarely at the base of trees or on dead branches;common on the dryer rock faces in canyon areas; 0--3000 m; Greenland; Alta., B.C., Man., N.B., Nfld., N.W.T., N.S. Ont. Que., Sask., Yukon; Alaska, Ariz., Colo., Conn., Idaho, Ill., Ind., Iowa, Maine, Mich., Minn., Mont., N.Mex., N.Y., N.Dak., Ohio, Pa., R.I., S.C., S.Dak., Tenn., Utah, Vt., Va., Wash., Wisc., Wyo.; Mexico (Nuevo León, San Luis Potosí); West Indies (Haiti); Europe; Asia; n Africa.

Orthotrichum anomalum has exserted capsules that are slightly constricted beneath the mouth and 1-stratose leaves. The most useful character in distinguishing this species from others is the emergent or exserted capsule with 8 long ribs alternating with 8 shorter ones.