Description: Thallus crustose, episubstratic, areolate to areolate-verrucose, yellowish, brownish yellow to orange-brown, often glossy, of 0.5-4 mm wide, contiguous and convex areoles developing on a black hypothallus, forming patches to 10 cm in diam., often delimited by a black prothallus. Cortex pale grey in upper part, 40-60 µm thick, with a 15-40 µm thick epinecral later; medulla white, I-. Apothecia biatorine, black, 0.5-3(-4) mm across, with an initially flat, then irregularly convex, epruinose disc, without a distinct proper margin. Proper exciple strongly reduced; epithecium bluish green-black, sometimes in part brown, N+ violet; hymenium colourless, 40-50 µm high; paraphyses coherent, strongly swollen in water, 4-5.5 µm thick at base, the apical cells 5-8 µm wide; hypothecium colourless in upper part, pale yellow-brown in lower part. Asci 8-spored, clavate, very thin-walled, with a K/I+ blue, tall tholus penetrated by a faintly amyloid apical cushion, the wall K/I-, surrounded by a blue outer layer, Lecanora-type. Ascospores 1-celled, hyaline, ellipsoid, 7-12(-15) x 3-5(-6) µm. Pycnidia dark brown, immersed. Conidia hyaline, bacilliform to thread-like, 6.5-10 x 1.5-1.8 µm. Photobiont chlorococcoid. Spot tests: cortex: K+ yellow or orange-red, C-, KC+ red, P- or P+ yellow; medulla K-, C-, KC+ red, P+ orange. Chemistry: medulla with alectorialic acid (major), alectorialin, barbatolic, roccellic and protocetraric acids (all accessory).
Note: an arctic-alpine, circumpolar species found on hard siliceous rocks in wind-exposed situations, most common in the Alps, much rarer in the mountains of southern Italy; when young, it is a facultative parasite of Sporastatia testudinea. A dubious record from Campania reported by Nimis (1993: 682) and by Ricciardi & al. (2000) is not accepted here. Calvitimela melaleuca (Sommerf.) R. Sant. is considered as an independent species by some authors: it was reported from the Alps by Jatta (1909-1911) without indication of locality, and is also known from the Alps of Switzerland and France.