Global occurrence: Eurasia – Europe | Americas – North America (incl Mexico) | Arctic.  Substrate: lichens, lichenized fungi | rock – calcareous, calciferous, basic.  Life habit: lichenized (mutualistic with algal photobionts).  Thallus: crustose (crustaceous) – endosubstratal, inconspicuous, immersed | crustose (crustaceous) – episubstratal – unspecified; [th marginal and upper surface] specific structures: absent.  Ascomata: absent | present; ascoma: apothecial, apothecioid – hymenial; ascoma [mm]: (low) 0.3 (high) 0.5 (max) 0.8.  Asci: lecanoralean; [asc] tholus: thickened; [asc] tholus amyloidity (iodine reaction): present; [asc] tholus amyloidity pattern: amyloid with acuate axial body towards the apex (= Bacidia-, Buellia-, Ramalina-types etc).  Ascospores: (median) 8.0; [asp] length [µm]: (low) 10.5 (high) 13.5; [asp] width [µm]: (low) 3.5 (high) 7.0; [asp] septa: present; [asp] septa: transversely septate; [asp] pigmentation: hyaline, colourless; [asp] perispore, epispore: not apparent.  Secondary metabolites: absent.  Primary photobiont: present, chlorophytaceous – trebouxiaceous, chlorococcoid.  Secondary photobionts (eg in cephalodia): absent.

Thallus endolithic, a grayish or whitish color being imparted to the rock. Kilias (1981) also mentions forms with a scant or more abundant production of small, tan areolae. Apothecia small, 0.3-0.8 mm, flat or becoming convex, black, dull, epminose, old apothecia rarely with an umbo; exciple radiate, outer part greenish black, inward from hyaline to violet-brown; epihymenium olive-brown to green-black; hymenium 50-70 μm, hyaline, upper part greenish; paraphyses 1.8-3.0 μm, tips to 8 μm and densely colored, easily separable; asci subcylindrical; spores broadly oblong, constricted at septum, 8-16 x 3.5-7 μm.

Reactions: C-, P-; epithecium, exciple, and hypothecium all K+ violet and HNOj+ violet; hymenium 1+ blue turning red, apical apparatus of the ascus remaining blue.

This species grows on calcareous rocks in full sun. It is a rare circumpolar arctic-alpine lichen, in North America being reported as far south as the Santa Catalina Islands in California.