https://italic.units.it/index.php?procedure=taxonpage&num=2330
Thelidium absconditum (Hepp) Rabenh.
Thallus crustose, endosubstratic, continuous, grey- or yellowish-white, sometimes delimited from conspecific thalli by black lines and forming mosaics....
hepp
https://britishlichensociety.org.uk/resources/species-accounts/thelidium-zwackhii
Thelidium zwackhii | The British Lichen Society
the britishlichensociety