Thallus with distinct marginal lobes to 1 mm broad, with short branches and widened toward tips; inner part verrucose with globulose verrucae, dark brown, shining; underside pale with dark edge.

Apothecia solitary or rarely a few per areola, immersed; margin persistent and proper exciple sometimes also showing; disk concave or flat, to 0.5 mm broad, brownish black, darker than thallus; hypothecium grayish; epihymenium yellowish brown; hymcnium 90-185 µm. I+blue; paraphyses slender, 2 µm, tips to 3 µm; spores very numerous, ellipsoid-cylindrical, 3-4 x 1.5 µm.

Reactions: K-, C-, P-.

This species grows on acid rocks, especially along shores, on boulders manured by birds. It is circumpolar arctic, in North America ranging south to Colorado.