Description: Thallus crustose-placodioid, episubstratic, areolate, the areoles brown-black, often faintly grey-pruinose, flat, the central ones 0.2-0.8 x 0.2-0.6 mm, the peripheral ones elongated and radiating, 1-2 x 0.3-0.5 mm, becoming narrower at tips. Cortex 9-12 μm thick, the uppermost layer dark brown, the rest colourless; algal layer continuous; medulla white, of densely intricate hyphae. Apothecia lecanorine, 0.2-0.4 mm across, 1-3 per areole, more or less raised, with a black, epruinose, concave to flat, rugose disc, and a thick but weakly prominent, often radially sulcate thalline margin concolorous with thallus. Epithecium brownish, 15-20 μm high; hymenium colourless, (65-)80-100 μm high; paraphyses more or less branched and anastomosing, 1.5-2 μm thick at base, the apical cells 2-4 μm wide; hypothecium colourless. Asci c. 200-spored, the apical dome K/I-. Ascospores 1-celled, hyaline, ellipsoid, (2-)3-4 x c. 1.5 μm. Photobiont chlorococcoid. Spot tests: cortex and medulla K-, C-, KC-, P-, UV-. Chemistry: without lichen substances.
Note: a silicicolous species described from Switzerland and also reported from Austria (Tyrol), whose ecology and distribution need further study. To be looked for in the Italian Alps.
Magnusson A. H. (1935) Acarosporaceae, Thelocarpaceae. - In: Rabenhorst G. L.: Kryptogamen-Flora von Deutschland, Österreich, und der Schweiz-. 2nd- IX. Die Flechten. Abt. 5- 1. Gebr. Borntraeger. Leipzig, pp. 1-318. – Public Domain