Description: Thallus crustose, endosubstratic or very thinly episubstratic, usually poorly evident, rarely of a few, dispersed, flat, thin areoles near the apothecia. Medulla I+ blue-violet (character difficult to observe due to the poorly developed thallus). Apothecia lecideine, black also when wet, strongly constricted at base, 0.6-1.4(-4) mm across, with a concave to convex, dull, epruinose or faintly pruinose disc, and a usually persistent, dull to shiny, often more or less undulate, sometimes vertically striated proper margin. Proper exciple 30-80 µm wide laterally, black in outer part, colourless or pale purplish brown within, the medullary part with crystals dissolving in K, C-; epithecium dark green, green-black or rarely dirty brown, 8-14 µm high; hymenium colourless or more rarely with a pale violet tinge in marginal parts, 37-65 µm high, I+ blue; paraphyses simple, rarely branched, the apical cells 3.5-5 µm wide, globose, with dark caps; subhymenium colourless 25-50 µm high; hypothecium colourless to rarely pale brown, 40-90 µm high. Asci 8-spored, narrowly clavate, thick-walled, with a K/I+ pale blue tholus and a strongly amyloid, thin apical cushion, surrounded by a I+ blue outer layer, Lecidea-type. Ascospores 1-celled, hyaline, oblong-ellipsoid, (6-)8-12(-16) x (2-)2.6-3.8(-5) µm, 2.3-3.7 tiems as long as wide. Pycnidia graphidoid, immersed in tiny whitish areoles. Conidia cylindrical, (6-)8.4-12.3(16) x 1-1.3 µm. Photobiont chlorococcoid. Spot tests: cortex and medulla K-, C-, KC-, P-. Chemistry: 4-O-demethylplanaic acid, sometimes with traces of planaic acid, or (more rarely) without lichen substances.
Note: a still insufficiently known species of the L. plana-group with narrower ascospores, found on siliceous rocks, usually at high elevations; European distribution poorly documented, with a few records from the Central Alps outside the Italian territory; to be looked for in the Italian Alps. According to Hertel (1999), most specimens identified as L. paratropoides, when chemically analyzed, will probably turn out to be L. laboriosa.