Vue dans le bois de Vincennes, pousse sauvage.
I don't think ALL pitting in barnacles is down to Pyrenocollema . But when it so evenly distributed and sized it is quite likely.
I was amazed that AI here recognised it.
It seems very common but this is my first encounter and I intend to follow it more closely.
Also see on nearby live Patella Photo 9 (A)
I suspect we might also see Pyrenocollema sublitorale** (photo 10 (B))
But I need to collect more photographs.
Many of the surfaces seen n these old barnacles (Semibalanus baloides) are abraded by the seawash,
.
http://www.lichensmaritimes.org/index.php?task=fiche&lichen=876&lang=en
**https://nature22.com/estran22/vegetaux/lichens/lichens1.html