1. Ptilium crista-castrensis (Hedwig) De Notaris, Comment. Soc. Crittog. Ital. 2: 283. 1867.
Hypnum crista-castrensis Hedwig, Sp. Musc. Frond., 287, plate 76, figs. 1-4. 1801
Plants dark green in deeply shaded sites, orange-golden to rusty in exposed sites. Stems 3-10 cm, usually hooked at apices, branches 0.3-1.5 cm, arising at right angles, hooked at apices or attenuate; rhizoids usually absent. Leaves tapering to apex, 2-3 mm. Seta 2-3 cm. Capsule red-brown, 1.5-2 mm; operculum apiculate. Spores 12- 16 µm.
Capsules mature fall. Coniferous forest floors, tundra, peatlands, deciduous forests, especially in boreal regions; low to high elevations (0-2000 m); Greenland; Alta., B.C., Man., N.B., Nfld. and Labr., N.W.T., N.S., Ont., P.E.I., Que., Sask., Yukon; Alaska, Colo., Conn., Idaho, Iowa, Maine, Md., Mass., Mich., Minn., Mont., Nebr., N.H., N.J., N.Y., N.C., Pa., S.Dak., Tenn., Vt., Va., Wash., W.Va., Wis., Wyo.; Europe; Asia.