Magnusson, A. H. (1929). A Monograph of the Genus Acarospora (Vol. 6, No. 17). Almqvist & Wiksells Boktryckeri: 163-164.
Thallus indeterminate, subsquamulose, red-dark brown/grayish-brown, squamules contiguous, verruciform or subpodicellate, irregularly rounded, always dark underneath. Apothecia crowded, solitary, disc dark brown/dark grayish-brown, plane or subconvex, scabrid. Hymenium thick. Cortex moderate above, cells large. Spores very thin, ellipsoid.
Squamules 0.5-1 mm large, (0.3-)0.5-1 mm thick, grouped or +/- scattered, the centre below blackish, loosely attached to the earth. No reaction with KOH or CaCl2O2.—Upper cortex 25-35 µ thick, transparent, exterior 9-12 µ gradually pale brownish yellow, amorphous stratum +/- developed, irregular, 10-25 µ thick. Cell-lumina fairly distinct in water, 3-5 µ large, irregularly angular or round, thin-walled. Gonidia 12-17 µ large, forming a dense, continuous, 100-200 µ thick stratum with very even surface, the lower limit gradually dissolved, stratum continuous also below hymenium. Medulla 300-500 µ thick, transparent, somewhat lax, hyphae +/- densely intricate, 2.5-3.5 µ thick, thin-walled, lumina +/- cylindric. Lower side corticated at the edges like the surface far in towards the centre, with 10-15 µ thick, blackish brown surface.
Apothecia immersed—only the youngest squamules sterile—disc 0.4-0.7 mm large, round, surrounded by the thallus as an even lecanorine margin.—Excipulum distinct, 15-25 u thick at the base, yellowish, only slightly widened at the surface and confluent with the cortex. Hypothecium 50(-100) u thick, opaque, sometimes +/- brownish and then still darker in KOH. Hymenium 120-150 u high, I+ blue, exterior 20-25 u rather bright brownish yellow, surface uneven. Paraphyses thin, (1-)1.5 µ thick, discrete in water, apices not or slightly swollen. Asci 100-115 X 17-25 µ large, clavate. Spores 200 or more, 3.5-4.5 X 1.8 µ, in KOH somewhat broadly ellipsoid.
Pycnidia not observed.
Habitat. On earth with A. scabrida and Biatorella groenlandica (n. sp.).
Distribution. Greenland. Danmarks ö, 1892 N. HARTZ. Two specimens (Chg.), called A. badiofusca.
A. groenlandica comes near A. scabrida and Novae Zemliae on account of the rough disc and the high hymenium but is separated from the former by thinner cortex, dark lower side, regular lecanorine, solitary apothecia, from the latter by the higher hymenium, larger cortical cells and bigger spores. A. groenlandica resembles a Lecanora species on account of the regular, thalline margin round the disc.