Thallus fruticose, weakly dichotomously branched, lobes flat or slightly canaliculate, to 3 mm broad; underside pale brown to white, smooth and glossy; upper side dark brown, olive-green, or yellowish green, smooth or rarely with transverse ridging; dull, marginal pseudo-cyphellae very distinct on outer parts of lower surface; laminal pseudocyphellae absent; marginal projections few and inconspicuous, to 0.5 mm long. Upper cortex paraplectenchymatous, 30-40 μ, medulla 70-110 μ, lower cortex paraplectenchymatous, 20-40 μ. Apothecia lateral marginal, substipitate, to 4 mm broad; disk brown, margin slightly crenulate, hymenium 30-60 μ, asci clavate to cylindrical; spores 8, round to subglobose, 3.5-6 x 3.5-5 μ.

Reactions: medulla I-, K-, C-, KC-, P-.

Contents: lichesterinic and protolichesterinic acids.

This specics grows on the tiwigs of Betula and Salix, occasionally on the ground. It is an amphi-Beringian species with a very restricted range in eastern Siberia and Alaska. The related C. subalpina Imsh. has indistinct marginal pseudocyphellae on the underside, is smaller, and contains protolichesterinic acid and two unknown substances. It is more southerly in distribution along the Pacific coast and a Point Barrow report could not be substantiated by Karnefelt (1979).