Brachymenium acuminatum Harv. in Hook., Icon. Pl. 1: 19. 1836.
Protologue: East Indies, Harvey.
Brachymenium filescens Bartr., J. Wash. Acad. Sci. 21: 292. 1931. Protologue: Costa Rica. Province of Alajuela, Cebadilla, alt. 700 m., Nov. 14, 1928, Valerio 209 (FH, US).
Plants minute, yellow-green, gregarious or in loose tufts. Stems slender, 2–10 mm long, epidermal cells quadrate, sparsely tomentose at base; rhizoids sparse at base, reddish brown, papillose roughened. Leaves 0.5–0.8 mm long, stiffly erect-appressed to imbricate when dry, concave, ovate to ovate-lanceolate; apices shortly acuminate; margins weakly bordered by long, narrow cells, entire, erect above, slightly reflexed below; costa percurrent to shortly excurrent, ventral superficial cells at base quadrate to rectangular; leaf cells lax and thin-walled throughout, upper cells elongate-rhomboidal, 40–90 x 10 μm, alar cells short-rectangular, 20–30 x 16–20 μm. Dioicous. Setae 10–30 mm long, red. Capsules 1.5–2.0 mm long, red, claviform to elongate-pyriform, constricted at neck, erect; opercula 0.3–0.5 mm long, conic; annuli compound, revoluble; exostome teeth reddish brown, thickly papillose, endostome yellowish, basal membrane to ½ the exostome teeth length, segments rudimentary to absent, cilia rudimentary to absent. Spores 10–14 μm, smooth to obscurely roughened. Calyptra not seen.