Plants slender, not distinctly polytrichoid. Stems simple. Leaves with a sheathing base and divergent limb; sheath ciliate on the shoulders, not hyaline-margined; limb serrate-toothed to the sheath (or ciliate near the base), with lamellae restricted to the adaxial surface of the costa; lamina 2-stratose, with sporadic 1-stratose patches, the adaxial layer of cells bulging-mammillose; lamellae serrate in profile, the marginal cells in section not differentiated, smooth. Capsule short-cylindric, terete, flaring at the mouth when old and empty, weakly contracted at the base, the long-tapering neck merging with the seta; exothecial cells without thin spots or pits; stomata present, confined to the neck; operculum conic; peristome none; columella flaring at the tip, persisting and elevated above the rim of the capsule. Calyptra naked. Spores papillose.
Northern Pacific Radiant distribution, nw North America, e Asia (Japan, e Siberia).
Diagnostic features of Bartramiopsis include the serrate lamellae, the ciliate sheath, the terete capsule, which is flared at the mouth and tapers toward the base, the absence of a peristome, and the naked calyptra. The genus occupies an isolated position in the family, and the gametophyte has a curious un-polytrichoid appearance. The bistratose lamina and the absence of even a rudimentary peristome have led to its association with Lyellia, but the capsule in that genus is strongly dorsiventral with 2 sharp angles, with a bowl-shaped disc at the capsule mouth and the blunted columella apex forming a “stopper” in the small central opening. In Bartramiopsis, the exserted columella is broadly flared, extends to the capsule rim, and persists long after the operculum is shed.