On calcareous rocks. Thallus of minute creamish to pale yellowish brown areoles, 0.1-1 mm diameter, coalescing into larger structures following joints and cracks in rock substratum and forming elongated patches 1-3 cm diameter. Upper surface convex, minutely cracked, surrounded and/or intersected by a thin, narrow, black prothallus, the whole lichen appearing piebald. Apothecia sessile, scattered, black, lecideine, convex; disc matt, epruinose, slightly roughened. Ascospores not seen (Galloway & Ledingham, 2012).
Thompson, J., 1997. American Arctic Lichens: The Microlichens.
Thallus thin or rarely moderately thick, subcontinuous or dispersed, ashy to bluish-ashy, dull; hypothallus indistinct. Apothecia single or conglomerate, small, 0.2-0.4 mm, or when confluent to 1 mm, adnate, base constricted, flat and marginate, becoming convex and immarginate; exciple black-violet to dark bluish, cells radial; disk black; hypothecium brownish above, hyaline below; hymenium 40-70 μm, partly or entirely blue; paraphyses coherent, gelatinous; spores oblong, 7-15 X 3-4 μm.
Reactions: medulla K—, C —, KC, I—; hymenium 1+ blue.
Contents: none reported.
This species grows on acid rocks. It is circumpolar but rarely collected, being known from the Arctic, Scandinavia, mountains of Europe, and in North America from Newfoundland, the Adirondack Mountains, the Rocky Mountains in Colorado, and northern Wisconsin (Brodo 1967).