Hypnum alleghaniense Müller Hal., Syn. Musc. Frond. 2: 502. 1851

Plants (3-)5-8(-10) cm. Secondary stem leaves 2-3.5 × 1.4 mm. Branch leaves ovate, 1.5-2 × 0.5-0.6 mm; margins coarsely serrate at apex; apex acute to acuminate; basal laminal cells 6-10 × 1-2 µm; medial juxtacostal cells short-rhomboidal, longest axis 45± to costa, 3-5 × 1-2 µm; apical cells elongate-rhombic, 3-5 × 1-2 µm. Sexual condition synoicous or autoicous.

Rock, logs, deeply shaded wet rock ledges, limestone cliffs, sandstone of Tsuga hardwood forests, mixed deciduous forests; moderate elevations; N.B., N.S., Ont., Que.; Ala., Ark., Conn., Ga., Ill., Ind., Ky., Maine, Md., Mass., Mo., N.H., N.J., N.Y., N.C., Ohio, Pa., S.C., Tenn., Vt., Va., W. Va., Wis.; Europe; Asia (China).

Thamnobryum alleghaniense is distinguished by the elongate-rhombic apical cells of the branch leaves, and by the longest axis of medial cells near the costa oriented at a 45± angle. The branches are incurved when dry.