1. Astomiopsis C. Müll., Linnaea. 43: 391. 1882.
Plants minute to small, often less than 6 mm high, scattered or loosely gregarious, yellowish green or yellow. Stems erect or curved-erect, simple or branched from the base, often with 1–3 sterile, julaceous or clavate branches arising from a subterranean rhizome; central strand present. Leaves strongly concave, crowded, appressed or imbricate; lower stem leaves small, bract-like, margins plane, entire or erose-crenulate, costa single or occasionally absent; upper stem and subperichaetial leaves shortly ovate to oblong-ovate or obovate, shortly acuminate, or broadly tapering to an obtuse apex, margins entire below, erose-crenulate to faintly serrulate above, costa single, subpercurrent to shortly excurrent; upper and median cells rectangular, rhomboidal, irregularly quadrate or trapezoidal, incrassate; basal cells rectangular, thin-walled; alar cells not differentiated. Autoicous or paroicous. Perichaetial leaves broadly oblong-ovate or obovate, obtuse to acuminate to short-subulate, costa sometimes ending in a smooth awn. Setae single, short to very short; capsules erect, immersed, emergent or shortly exserted, broadly ellipsoidal to short-cylindric or subglobose to cupulate upon dehiscence; exothecial cells quadrate to trapezoidal or rectangular, moderately thick-walled; stomata present at the base of capsules, superficial; opercula bluntly conic to obliquely short-rostrate; annuli slightly differentiated, in 2–4 rows of quadrate cells, persistent; peristome teeth absent. Calyptrae small, cucullate or mitrate, smooth. Spores spherical, yellow to golden brown, smooth or minutely papillose.
The genus, consisting of six species in the world, has been known from Africa, Asia, Mexico, Central and South America. Only one species is known from China.