Dimelaena oreina (Ach.) Norman forma oreina

    Thallus crustose, centrifugal development, round, placodioid, margin lobate, lobes radiating, flat or slightly convex, areolate towards the center, lobes and areoles clearly contrasting with underlying prothallus within cracks, overall colour variable according to chemotypes, greyish to glaucous, grey-yellowish, grey-greenish, yellowish (most often the yellow tinge is visible). Apothecia 1 (2-3)/areole, lecanorine, usually numerous, immersed in areoles at first, then slightly protruding, disc black, flat to slightly convex, exciple thin, concolorous to the thallus. Ascospores broadly ellipsoid, brown, 1-septate, constricted at septum level (wool ball-shaped), 9-15 x 5-8 µm. Seven chemoptypes have been described, 5 in Europe.

Chemotype I : C-, K+ yellow, KC-, Pd+ yellow > red.

Chemotype II : C+ red, K-, Pd-.

Chemotype III : C-, K-, KC-, Pd-.

Chemotype IV : C+ red, K+ yellow, Pd+ red.

Chemotype V : C-, K+ yellow, KC-, Pd+ orange = Chemotype oreina (The most common in France).

    Saxicolous species, on slopong or vertical walls of well-lit and exposed siliceous rocks. Mostly montane.