Thompson, J., 1997. American Arctic Lichens: The Microlichens.
Thallus sometimes in small masses of rounded or angular areolae, and separated by cracks, or dispersed, rust-colored or dark orange-brown to yellowish; underside pale or darkened at edges; cortex 20-35 µm. Apothecia mostly 2-8 per areola, immersed and with the ostiole appearing as dots or narrow disks; disk 0.1-0.2 mm, rarely to 0.7 mm broad, dark brown or blackish, lacking proper exciple around it, although there is a 15-30 µm proper exciple within in section view; hypothecium opaque; epihymenium dark rusty; hymenium 120-170 µm, globular in shape with paraphyses convergent toward disk, 1+ yellowish red; paraphyses 1-1.5 µm, tips not thickened; spores very numerous, ellipsoid, 3-3.5 x 1.2—1.6 µm.
Reactions: cortex K—, C —, P—.
This species grows on acid rocks rich in iron. It appears to be circumpolar arctic and alpine, according to Magnusson (1929), but the only North American material seen is found in the eastern Arctic and south to the White Mountains of New Hampshire.
While this species is sometimes considered an ecological variant of A. smaragdula, it lacks the norstictic acid in the cortex and the K+ reaction.