Encrusting "crusty" lichen, green thallus, yellow/green apothecia
No identification made yet.
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I am afraid I don't have a name for this. There are a huge number of crustose lichens and it may well be a species I don't know, or one that cannot/should not be named from photographs.
However, for a chance of identification, especially of crustose species, photographs have to be high definition to show the often minute surface features on which identification depends, and I am afraid this photograph doesn't have that definition. Focus must be pin sharp and there must be absolutely no camera movement. Sorry.
It occurs to me that this could be Lecanora polytropa, which can fit "green thallus, yellow/green apothecia", and is common on nutrient-poor rocks. But this can be no more than a guess, imo.
Lat/Lng: 55.74892, -4.91504
OS grid ref: NS171544
Found on the top of rocky shore in western Scotland. Also noticed this lichen on wooden fence posts close to the shore.