Forum Flora Germanica

Slovenia, Karst, imagine a little more vivid green (blue maybe at some point), close enough but not there jet.
http://agrozoo.net/jsp/Galery_one_image ... c274426844

Edit: A candidate: https://www.irishlichens.ie/pages-lichen/l-234.html
green one: https://www.afl-lichenologie.fr/Photos_ ... nigrum.htm

Looks like a match.
(I don't know it).
German PDF about this genus: Placynthium in den Alpen und Karpaten sowie in benachbarten Gebieten (2005
(including P. nigrum + similar species). They say, if this prothallus is not developed and those lichen not growing typically, than they are difficult to determine.
https://blam-bl.de/images/Herzogia_20/H ... a_full.pdf