Thompson, J., 1997. American Arctic Lichens: The Microlichens.
Thallus yellowish white to yellowish gray, sometimes little more than a white stain on the wood, continuous, rough to verrucose or very thin. Apothecia large, 0.6-1(-2.9) mm, sessile to slightly constricted, often crowded and angular; margin thick or thin, smooth, becoming flexuous, concolorous with thallus; thalloid exciple with small crystals in the medulla not extending into the cortex; cortex gelatinous, in-spersed; disk dark red-brown, reddish orange, or becoming black, shiny; epihymenium not granular or inspersed, red-brown; hymenium 60-85 μm; spores 8, hyaline, simple, ellipsoid, (10-)13-17(-18) x 6-9 μm.
Reactions: medulla and margins K+ yellow, C—, P—.
Contents: atranorin and unknown triterpenoids.
This species grows on logs and rocks along sea coasts. It is common on the northeastern and Pacific coastal areas, reaching the Arctic in the Aleutian Islands and on St. Paul Island in the Bering Sea.