Plants rather robust, 3–5 cm high, yellowish green above, brownish below, in loose tufts. Stems fasciculate, branched. Leaves somewhat crisped and contorted when dry, spreading when moist, 4.0–6.5 mm long, lanceolate to linear lanceolate from an oblong-ovate base, plicate below, with acuminate apices; costa single, strong, extending to the leaf apex; margins recurved below, with large remote teeth above; upper leaf cells unistratose, round-quadrate to subquadrate, 4.8–6.4 µm wide; median leaf cells quadrate, 6.4–9.6 µm wide; basal cells elongate, 24–56 µm × 11–16 µm, with straight walls; cells conspicuously bulging on the adaxial surfaces at middle and upper parts of leaves. Autoicous. Perichaetial leaves similar to stem leaves. Setae erect, 8.5–12.0 mm long; capsules oblong-ellipsoid or oblong-ovate; peristome teeth linear-lanceolate, bifid to the base, densely papillose, without perforation; opercula with long, erect beaks. Calyptrae mitrate, reaching to middle or lower part of capsule, plicate, lobed at base. Spores yellowish brown, spherical, 10.0–13.2 µm in diameter.

Type. China: Sichuan, Ya-an Co., Bao-xin, on rocks, alt. 1100 m, Q. Li 11497 (holotype IFSBH).

Specimen examined: see the type citation above.

Habitat: on rocks; Distribution endemic to China.

Ptychomitrium mamillosum is characterized by having leaves with dentate margins and conspicuously conic-bulging cells on the adaxial surfaces at the upper and middle parts of the leaves.

Illustrations: S.-L. Guo, T. Cao & C. Gao 2000 (Figs. 1–11).