Helicophyllum Brid., Bryol. Univ. 2: 771. 1827.
Medium-sized plants in mats. Stems creeping, irregularly branched, central strand present, densely reddish‑brown tomentose on underside of stem; rhizoidal initials clustered below leaf insertions and scattered along the stem; axillary hairs 2–3‑celled, basal 1–2 cells short, quadrate, brownish‑red, apical cell enlarged, oval to oblong, thin‑walled, hyaline. Leaves dimorphic: lateral leaves wide‑spreading when wet, often complanate in 2 rows, inrolled contorted when dry, lingulate to oblong‑ovate; apices broadly rounded to obtuse; margins narrowly recurved, bordered by smooth, linear cells, entire; costae single, ending near the apex; upper cells quadrate to rounded‑hexagonal, thin‑walled, bulging mammillose, or stoutly unipapillose, dorsal leaves oblong to ovate, half the size of lateral leaves, otherwise similar; ventral leaves small, nearly buried in tomentum, lanceolate to triangular‑acuminate; upper leaf cells short‑rectangular, thin‑walled, pellucid, unipapillose. Dioicous. Perigonial buds swollen, terminal on stem or on short lateral branches; leaves ovate; costae percurrent to short excurrent; cells elongate below, short‑rectangular above, smooth or weakly papillose; paraphyses present. Perichaetia at ends of stems or branches, greatly enlarged and differentiated; leaves oblong‑lanceolate; acuminate; margins revolute to near apex, serrulate above; costae shortly excurrent; cells elongate, smooth; paraphyses absent. Setae very short to apparently absent. Capsules immersed, erect, symmetric, abruptly incurved at mouth, cupulate to oblong, smooth when dry, irregularly dehiscent; stomata absent; opercula flat to slightly convex, at times shortly apiculate, irregular at margins, inserted within the capsule mouth; peristome absent. Spores papillose. Calyptra absent (?).