Preslia, 37: 241, 1965.. Basionym: Gyalecta geoica f. trivialis Willey ex Tuck. - Synopsis N. Amer. Lich. (Boston) 1: 220, 1882.
Description: Thallus crustose, very thinly episubstratic, grey-green to almost black, c. 100 μm thick. Apothecia short-lived, round, completely immersed in the thallus or in the soil, 0.2-0.4 mm across, 0.1-0.2 mm tall, with a deeply concave, pale brown disc, and a pale yellowish white, smooth, persistent proper margin. Proper exciple colourless, laterally up to 60 µm wide, of conglutinated, parallel hyphae; epithecium indistinct, colourless; hymenium colourless, 90-100 µm high, I+ yellowish, K/I-; paraphyses dense, slender, indistinctly septate, simple or forked, the apical cells globose or clavate; hypothecium very thin, colourless. Asci 8-spored, long-cylindrical, thin-walled, the upper part with a distinct, K/I- apical dome penetrated by a long, narrow tube extending from the endoascus, with 1-2-seriately arranged spores. Ascospores 3-septate, hyaline, fusiform with pointed ends, straight or slightly curved, 20-28 x 5-6 µm, with very thin walls and septa. Photobiont chlorococcoid, the cells 6-12 µm across. Spot tests: thallus K-, C-, KC-, P-. Chemistry: without lichen substances.
Note: on clay soil under moist conditions, sometimes on humid siliceous rocks and epilithic mosses; known from a few stations in the Alps (Austria, Germany), but probably overlooked. To be looked for in Italy.
Growth form: Crustose
Substrata: soil, terricolous mosses, and plant debris