Thompson, J., 1984. American Arctic Lichens: The Macrolichens.
Thallus foliose, lobate, the lobes elongate with small lobules 2—4 mm broad, concave, the margin coarsely undulate, entire not swollen; upper surface smooth not glossy, lacking isidia, dark olive-green to blackish; lower surface paler with groups of hapters. Apothecia numerous, superficial or marginal, sessile, to 1.5 mm broad; disk flat to convex dark red to red-brown, smooth; margin thick, entire or crenulate; proper exciple thick and paraplectenchymatous; hymenium 85-105 µ, 14-blue; paraphyses simple or branched clavate at apices; asci clavate; spores 8, linear oblong with rounded ends, not or slightly constricted at septa, 3 septate, hyaline, 17-30 x 6.5-9 µ.
This species is calciferous and grows on soil or rocks. It is primarily European and North American but has been reported from Japan. It is arctic-alpine and in North America occurs south to the Gaspe Peninsula and to Alberta and Saskatchewan.
There are two varieties in this species, var. granulosum Degel. has the thallus with globular isidia on the surface and is the more arctic variant. Var. undulatum, the typical material lacks the isidia and is more southerly.