Barbula convoluta Hedw., Sp. Musc. Frond. 120. 1801.
Tortula convoluta (Hedw.) Gaertn. et al., Oekon. Fl. Wetterau 3(2): 92. 1802. Streblotrichum convolutum (Hedw.) P.-Beauv., Prodr. Aethéogam. 89. 1805. Protologue: Germany, France, Switzerland, England. Ad aggeres et fossas Germaniae, Galliae, Helvetiae, Angliae.
Plants small, yellow-green above, brown below, in tufts, 2–5 mm high. Stems red, erect, irregularly branched, sclerodermis and central strand present; rhizoids distributed at base of stems, red, smooth. Axillary hairs 5–7 cells long, all cells hyaline. Leaves 1–1.6 mm long, oblong-ligulate to oblong-lanceolate, or lingulate, crowded on stem, erect-incurved, contorted or spirally twisted when dry, erect-spreading to spreading when wet, grooved along the costa on ventral surface, ventral epidermal cells elongate; apices rounded obtuse to broadly acute, not apiculate; lamina unistratose; margins entire, recurved below, plane above; costa ending 6–8 cells below the apex, papillose at back on dorsal surface by simple papillae, guide cells well-developed, ventral stereid band absent or weakly developed, dorsal stereid bands well-developed, ventral surface layer not enlarged; upper cells rounded quadrate, subquadrate, or oblate, 7–10 μm, firm-walled, densely pluripapillose by massive, compound papillae, inner basal cells oblong, short to long-rectangular, firm-walled, smooth, 20–40 x 8–16 μm, alar cells not differentiated. Dioicous. Perichaetia leaves convolute-sheathing, greatly enlarged. Setae smooth, 10–20 mm long, yellow to yellow-brown. Capsules cylindrical, erect, 1–2 mm long, smooth; exothecial cells short-rectangular, firm-walled; stomata in neck; opercula erect, long-rostrate, 1–1.5 mm long; annuli well-developed, vesiculose; peristome red, basal membrane high, teeth spirally twisted, to 1 mm long, densely spiculose. Spores 6–8 μm, smooth. Calyptrae cucullate, smooth, to 2.0 mm long.