foliose, forming rosettes on rock surfaces, the lobes narrow, to 2 mm broad, slightly channeled as the previous species; upper side bronzy brown to black brown, shining or dull; underside pale or becoming brown, with scattered black rhizinae. Apothecia
at the tips of short lobes, more or less central on the thallus, to 7 mm broad; margin thin, inflexed, irregularly thickened, disk of the same color as the thallus, slightly shining, smooth, concave; epithecium
brownish, hypothecium pale; hymenium
45-55 μ; spores
8, hyaline, simple, ellipsoid, 8-10x4.5 μ; spores
8, hyaline, simple, ellipsoid, 8-10 x 4.5 μ; Conidia
cylindrical or the center thickest, not the ends, 3-4 x 1 μ.
Reactions: K- , C- , KC- , P-.
Contents: a-collatolic acid.
Growing on rocks and gravel in open dry places, this is a circumpolar, arctic-alpine species, in North America ranging from Labrador to Alaska, south to New York, Colorado, and Washington.