Stems: 2–5 mm. Leaves: 1–2.5 mm, distal laminal cells mostly isodiametric, 1:1, with a few cells 2:1 or transversely elongate, areolation somewhat irregular, proximal cells longer. Seta: 0.5–2 mm, flexuose when dry. Capsule: spherical to short-ovate, 0.4–0.6 mm. Peristome: absent. Spores: 6–10 µm.
Moist, acidic boulders, montane, predominantly alpine. B.C., Alaska, Oreg., Wash., e Asia (Japan).
The spherical or short-ovate capsules absent peristome teeth and the somewhat shorter distal laminal cells distinguish Brachydontium olympicum from B. trichodes. This is a circum-North Pacific montane species, which should be sought for in coastal areas of Siberia.