2. Callicostella (C. Müll.) Mitt. 强肋藓属 qiang-le xian shu
J. Proc. Linn. Soc., Bot., Suppl. 1: 136. 1859. Hookeria sect. Callicostella C. Müll., Syn. Musc. Frond. 2: 216. 1851.
Plants often slender, medium-sized, mat-forming, light yellow, dark green to dark brown in color. Stems long creeping, subpinnately branched, rhizoids dense, secondary stems 3–5 cm long, in cross section with several layers of colored, slightly thickened cortical cells surrounding a parenchymatous core, central strand absent. Leaves complanate, forming dorsal, lateral, and ventral rows, flexuous and plicate when dry, ovate to oblong-lanceolate, rounded or abruptly short-acuminate, toothed above; costae double, strong, reaching leaf apex; leaf margins plane, asymmetrically folded on one side at leaf base, without differentiated borders, irregularly serrulate above, entire near base; leaf cells oval-hexagonal, mostly papillose, elongate, smooth below. Setae lateral, smooth or weakly papillose distally; capsules ovoid-cylindrical, horizontal to inclined, strongly constricted at mouth; exostome teeth cross-striate, with wide median furrows; opercula conic-rostrate. Calyptrae mitrate, laciniate at base. Spores spherical.