Verrucaria maas-geesterani Servít

Lichenised. Poorly known taxon.
Substrate:
Altitudinal distribution: montane belt (potential vegetation: deciduous forests dominated by Fagus sylvatica and closed coniferous forests with Picea abies)
Note: a species which is similar, and probably closely related to V. margacea, with an epilithic, partly rimose, blackish-brown (black in the wet state) thallus, superficially with small black warts, in section with a carbonised basal layer, ascomata (to 0.3 mm in diam.) black and hemispherically protruding, but with a thin thalline layer in the lower part, involucrellum tightly adpressed to the perithecial wall and reaching down to the base, where it fuses with the basal layer, 8-spored asci, and broadly ellipsoid, simple ascospores (20-28 × 13-16 μm); on submerged siliceous rocks in streams, only known from the type locality in the Western Alps (Switzerland).
Switzerland: Ticino;