Lecanoromycetes, Ostropomycetidae, Agyriales, Trapeliaceae

Thallus crustose, areolate or cracked–rimose: photobiont green, Chlorococcaceae.
Ascomata apothecia, lirellate to round or somewhat angular, disc slit-like.
Proper exciple of dark-brown, conglutinate, anastomosing and radiating hyphae
Hymenium colourless I+ blue, 65–59 µm tall; epihymenium often poorly defined, brownish.
Hamathecium of paraphyses.
Hypothecium pale- to dark-brown.
Asci cylindrical, Rimularia or Trapelia -type; ascospores colourless, ellipsoidal, halonate or not.
Conidiomata pycnidia (often not seen), black, minute, immersed;conidia, short rods.

Lithographa is a genus of seven saxicolous species that until recently was represented only by the type species (L. tesserata (DC.) Nyl.), known only from the Northern Hemisphere. However, recent work has identified a number of other species in the Southern Subpolar Region (Hertel & Rambold 1990, Fryday 2004a; Coppins & Fryday 2006, Fryday & Coppins 2007).
The genus is closly related to Rimularia, from which it is separated by its lirallate apothecia. However, in some species (e.g. L. graphidioides) both round and lirellate apothecia can be found on the same thallus, whereas some species of Rimularia (e.g., R. gyrizans, R. sphacelata) have gryrose apothecia that can become almost lirellate. Some species of both genera also show some similarites to Trapelia and it is probably that a thorough revision of these genera will result in a revised generic delimination.
It is also probable that the two species with submuriform ascospores (L. serpentina and L. skottsbergii) should be included in a separate genus