Ditrichum ambiguum Best, Bull. Torrey Bot. Club 20: 117. 1893. Type. U.S.A., Washington, Mason County, Piper s.n.
Plants small, 3–15 mm high, dull green to yellowish. Leaves 2.0–2.5 mm long, erect to erect-flexuous, with spreading points, ovate-lanceolate to lanceolate, subulate-acuminate; margins narrowly recurved, entire below, serrulate at apex; costa percurrent; cells firm-walled to incrassate; lower cells long-rectangular, 25–27 µm long; upper cells short-rectangular, 15–17 µm long. Dioicous. Setae 8–9 mm long, red; capsules erect, cylindric, 1.8–2.0 mm long; opercula high-conic, blunt; peristome teeth 500–800 µm, split nearly to the base into 2 terete, filiform, red, densely spiculose, obliquely twisted divisions. Spores 12–13 µm, smooth.