Thallus mostly immersed in the substratum, where present reduced to the immediate vicinity of apothecia and sheltered spots (underside of the rock), creamy-white, smooth, cracked-areolate; epinecral layer often present, 5–10 µm thick; medulla I+ violet. Photobiont chlorococcoid; cells 9–12 µm diam.
Apothecia black, lecideine, 0.8–1.5(–2.0) mm diam., ± flat, orbicular; disc ± flat, becoming convex and irregularly fissured when overmature: proper margin thin (0.05 mm wide), barely raised, becoming excluded in mature apothecia, in section poorly developed; pseudothalline margin usually present, thick (up to 0.2 mm wide) appearing pruinose due to thin (5–10 µm thick) epinecral layer. Hymenium 170–200 µm tall, with large oil globules (10–30(–40) × 10(–15) µm) in the upper hymenium that dissolve in K; paraphyses 1–1.5 µm wide, branched and anastomosing, with distinctly swollen apices (up to 5 µm) and pigmented caps; epihymenium 25–50 µm tall, dilute brown to olivaceous-brown (K± olivaceous or blue-black in patches). Asci cylindrical, c. 100 × 30 µm, Porpidia-type, no mature asci seen; ascospores simple, pigmented, 8 per ascus, 25–30 × 12–15 µm. Hypothecium hyaline to pale straw coloured.
Conidiomata: not observed.
Chemistry: No substances by TLC.
Distribution and Ecology: Known only from the type collection, which is from an apparently loose, angular piece of crystalline granite from the summit of Mt. Adam on West Falkland. Dactylospora australis Triebel & Hertel occurs on the apothecia of the type collection but no other species are present on the piece of rock. However, other species collected from the vicinity include Lecanora xantholeuca (Müll. Arg.) Hertel, Lithographa graphidioides (Cromb.) Imshaug ex Coppins & Fryday, Micarea incrassata Hedl., Poeltidea pertusa and Thamnolia vermicularis (Sw.) Schaer.
Remarks: In apothecial characters, this species closely resembles the type species of the genus, P. perusta. However, it differs from that species in the lack of a well-developed thallus, and the apothecia with a hymenium containing large oil globules.