Bryum rudimentale Allen nom. & stat. nov.

Bryum insolitum var. brachycarpum Bartr., J. Washington Acad. Sci. 24: 473. 1934. Protologue: Costa Rica. [San José:] Tiribi, 1100 m., Oct. 28, 1933, A. Alfaro 21 (NY, US).  

Plants small, silvery‑green, in loose tufts, 6–7 mm high; rhizoids papillose, not matted. Leaves to 1.0 mm long, imbricate with erect or recurved apices when dry, imbricate when wet, concave, not decurrent; apices broadly ovate, apiculate to filiform‑acuminate; margins plane or recurved below, not or weakly bordered, nearly entire; costae slender, percurrent or excurrent; upper cells elongate, hyaline, firm‑walled, basal cells sub‑quadrate to short‑rectangular, green, thick‑walled. Dioicous. Setae 10–25 mm long, red. Capsules 1–2.5 mm long, ovate to oblong, erect, light-brown becoming red with age; exothecial cells below the mouth strongly differentiated in 10 or more rows; opercula 0.3‑0.5 mm long, conic-apiculate; annuli compound and revoluble; exostome teeth lightly papillose, light-brown, 200–450 μm high, endostome yellowish to hyaline, basal membrane high, to _ the exostome length, segments and cilia rudimentary to absent. Spores 10–14 μm, smooth to faintly papillose. Calyptra not seen.