Thompson, J., 1984. American Arctic Lichens: The Macrolichens.
Thallus of tiny radiating lobes, flat, longitudinally grooved and striated, rarely smooth; 2-6 mm long, 0.2-0.4 mm broad, the tips broadened to 0.8 mm; isidia on the upper surface globose or cylindrical, becoming flattened; underside pale; upper side dark olive brown, rhizinae pale; interior hyphae longitudinally extended, those in the center cylindrical, those toward the margins ellipsoid, loosely arranged. Apothecia to 1 mm diameter with thal-loid margin; disk brown; hymenium 80-125 μ thick, hyaline, the upper part brown; subhy-menium hyaline, 40-70 μ, of ellipsoid cells in radiating rows; pseudoexcipulum with large, broadly ellipsoid cells; paraphyses septate, simple or sparingly branched, 2 μ thick, the tips broadened to 7 μ, often moniliform; asci 55-58 x 11.5-13 μ spores (8-) 12-16, hyaline, 1-celled but frequently with cytoplasmic bridges and appearing 2-celled, 7-10 x 4-6 μ.
This species grows on rock faces which are temporarily covered with running water, sometimes on vertical cliffs. It is known from Sweden, Greenland, and arctic Canada. It ranges south to British Columbia.