Thompson, J., 1997. American Arctic Lichens: The Microlichens.
Thallus thin, light gray to gray-green, rarely brownish, continuous or of flat, scurfy, or thick rugose areolae, dull or glaucous. Apothecia sessile, to 0.85 mm; margin of same color as thallus or more brownish, entire to becoming excluded, its cortex 1+ blue; exciple brownish exterior, hyaline within; disk black or sometimes brown at first, flat to becoming convex; hypothecium hyaline, 1+ blue; epihymenium red-brown; hymenium 70-100 μm, hyaline; paraphyses 2-3 μm, tips 4-6 μm, tips slightly darkened and in the dispersed pigment of the epihymenium; asci clavate; spores polari-locular, lumina angular, then soon round, porus disappearing, septum well developed and tips thin-walled, 17-24 x 10-12 μm.
Reactions: thallus K—, C —, KC—, P—, I—.
This species grows on twigs of Betula, Alnus, Populus, and Salix. It is circumpolar subarctic, but the range in North America is very poorly known.
This species is very close to R. archaea but with slightly different spore shape and more rounded locules when young than those of R. archaea, which are more angular. The thallus is also more arav-green than brown and is more developed than that of R. archaea, being continuous or composed of discrete flat or rugose areolae rather than chinky-areolate or disappearing or of small granules (despite the name, which was based on the superposed thallus of a granular lichen in the type specimen, according to J. W. Sheard).