Thompson, J., 1997. American Arctic Lichens: The Microlichens.
Thallus ashy or white, thin, uneven to granulose, commonly nearly obsolete, mostly within wood. Apothecia brownish black to black, dull, 0.3-0.5 mm, flat to convex, becoming nearly globose; exciple exterior dark, interior pale; hypothecium pale; epihymenium brownish to olivaceous; hymenium 40 µm, hyaline, upper part darker, 1+ blue turning red, K—; paraphyses coherent, the tips not thickened; asci clavate; spores fusiform to fusiform-bacillar, tips blunt, 3-septate (rarely 1-septate). (Description after Malme, I.e.)
This species was described from material on rotting wood collected on the Vega expedition from several localities along the north coast of Siberia. As it may well occur in northern North America, I have included it in the key.
Malme noted that this species is quite similar to B. subfuscula, with a different substratum, darker apothecium, and narrower spores.