Thallus areolate, up to 10 cm diam.; hypothallus well developed, black; areolae up to 1.2 mm diam., medium brown, dull to shiny, with a grey to black and somewhat sinuous margin, scattered to contiguous, more or less orbicular, plane to deeply concave, peltate; medulla KI–. – Apothecia up to 1 mm diam., black, epruinose, orbicular, remaining more or less plane, distinctly marginate; excipulum pale brown in inner part, containing crystals dissolving in K, rim brownish black, K+ red; hypothecium dark brown, K–; hymenium colourless; epihymenium medium brown, containing crystals dissolving in K, K+ red; ascospores 2 per ascus, eumuriform, dark greenish brown, 40–50 × 18–32 µm. – Conidiomata not seen.
Stictic acid; spot tests: medulla PD+ orange, K+ yellow, C–.
On acidic, exposed, sloping rock surfaces near river. In Norway (and Europe) known from a single locality (Hallandsfoss in Valle, Aust-Agder, 1955).
Resembles a luxurious R. rittokense, but that species has 1-septate ascospores, 8 in the ascus, and contains barbatic acid (in Norway; a stictic acid chemotype is known elsewhere)