in Carroll, Nat. Hist. Rev. Quart. J. Sci., 6: 533, 1859.
Distribution: N - TAA (M: Brackel 2016)
Description: Thallus inapparent, not lichenized, developing inside the thalli of Diplotomma alboatrum and D. chlorophaeum. Apothecia arthonioid, immarginate, black, dull, rounded to slightly oblong–irregular ellipsoid, 0.1-0.2 mm wide, flat to finally slightly convex, crowded in small orbicular patches on the host thallus. Proper exciple very poorly developed: epithecium greenish brown, K+ olive–green; hymenium colourless, 30-60 μm high, I+ blue, K/I+ blue; paraphysoids branched and anastomosing, 1.3-3(-3.5) μm thick, the apical cells only slightly swollen, up to 4(-5) μm wide; hypothecium dark reddish brown in upper part, colourless in lower part, 35-65 μm high, K+ olive–green. Asci 8-spored, broadly clavate to ovoid, semi-fissitunicate, with a large apical dome and a distinct ocular chamber, Arthonia-type. Ascospores 1-septate, at first hyaline but soon turning pale brown and verruculose, ovoid to oblong-ellipsoid, 12-17(-18) x 5-6(-7) μm. Photobiont absent. Spot tests: thallus K-, C-, KC-, P-, UV-. Chemistry: without lichen substances.
Note: a lichenicolous fungus growing on epilithic Diplotomma-species, whose distribution in Italy is still poorly known.