Plants large, green to dark green, becoming brown to reddish brown with age. Stems to 6 cm, sometimes matted with whitish rhizoids. Leaves 5-9 × 0.8-1.6 mm, densely imbricate, lingulate to lanceolate, plane to slightly keeled and concave, obliquely transversely undulate, often with rows of teeth on undulations on abaxial surface, the apex attenuate; costa subpercurrent to percurrent, with abaxial teeth along the undulations in distal half; lamellae 4-6, laxly spreading, 2-4(-6) cells high; median leaf cells 24-27(-30) µm wide, rounded to irregularly angled, weakly convex on both surfaces, thick-walled, strongly collenchymatous with trigones, smooth or usually with minute, rounded or striate papillae on abaxial surface. Sexual condition dioicous; male plants as large as females, perigonial bracts small, imbricate, ovate or suborbicular, often more than one perigonial bud in sequence per shoot. Seta 1-3 per perichaetium, 1.5-4 cm, reddish brown. Capsule 4-7 × 0.5-1 mm, usually somewhat curved and inclined, rarely straight and erect; operculum 2-3.5 mm. Spores 12-19 µm.
Capsules mature summer (Jun-Aug). Soil, humus, mostly shaded habitats; often wet banks along streams or sometimes at margins of fens and swamps; low to high elevations; N.B., Nfld. and Labr. (Nfld.), N.S., Ont., P.E.I., Que.; Ark., Del., Ill, Ind., Iowa, Kans., Ky., La., Maine, Md., Mass., Mich. Miss., N.H., N.Y., N.C., Ohio, Pa., Tenn., Va., W.Va., Wis.; e Asia (China, Japan).