Thompson, J., 1984. American Arctic Lichens: The Macrolichens.
Thallus bordered by a distinct black hypo thallus, areolate-crustose, yellowish gray or bluish gray, marginally much paler; hypothallus visible between the angular areolae, which range to 0.6 mm broad, 0.4 mm thick, the surface dull, flat; upper cortex 25-50 μm thick, gray, opaque, the outer 4-6 μm dark olive-brown, hyphae more or less vertical, 5-6 μm in diameter; algal layer more or less continuous; medulla 200-250 μm thick, gray with granules, hyphae more or less vertically oriented. Apothecia common, immersed, separated from thallus by a crack; proper exciple carbonaceous, very variable in thickness; disk about level with thallus, black, broken up into sections by deep cracks, very uneven; hypothecium 35-50 μm thick, gray, not clearly differentiated; hymenium 70-125 μm, hyaline, the upper 10-20 μm pale blue-green, dark green, or olive-brown; paraphyses 1.7-2 μm, tips 2.5-3 μm and dark green; asci broadly clavate, 65-90 x 17-25 μm; spores very numerous, 3-4.5 x 3-3.5 μm. Conidia not known.
Reactions: thallus K—, C+ reddish cortex and medulla, P—; hypothecium and hymenium 1+ dark blue.
This species grows on siliceous rocks and cliffs. It is an arctic-alpine species, much more rare than S. testudinea, known in Europe from Scandinavia, the Alps, the Pyrenees, and Carpathian Mountains, from Asia Minor, and in the Arctic from Jan Mayen, Spitzbergen, Novaya Zemlya, the Bering Strait area, and Greenland. In North America it is known from Ellesmere Island and other localities in the eastern Canadian Arctic, south to Montana and Colorado, and on Mt. Shasta, California.