7. Crossidium Jur., Die Laubmoosflora von Oestrreich-Ungarn. 1882.
Plants tiny, yellowish green to reddish brown, in low gregarious or thin tufts. Stems very short, mostly buried in soil, simple; central strand present. Leaves imbricately appressed when dry, slightly spreading when moist, broadly ovate to rounded ovate or shortly triangular, concave, abruptly to broadly acute at the apex; costa slender, shortly excurrent as an apiculus or excurrent in a short, smooth, hyaline awn; superficial cells of upper ventral costa forming a group of separate, often branching, filaments; in cross section a dorsal stereid band present; margins entire, incurved; upper leaf cells subquadrate to rounded elliptic, thick-walled, without papillae or papillose; basal cells rectangular, thin-walled. Dioicous or monoicous. Outer perichaetial leaves similar to stem leaves, inner perichaetial leaves smaller. Setae elongate, slender, more or less straight; capsules oblong-ovoid, erect or curved; annuli differentiated, of 3 rows of cells, persistent or deciduous; peristome teeth 16, divided into 32 linear-lanceolate segments, papillose, twisted counterclockwise, rarely straight; opercula conic, obliquely short-rostrate. Calyptrae cucullate, smooth. Spores small, spherical, yellowish brown, smooth or finely papillose.
There are 13 species currently recognized for the genus in the world. Most of the species occur in northern temperate regions with dry climates and basic soil. One species is known from China.