Black; shiny; looks like oil. On rocks regularly covered by the sea at high tide.
Caution: Do NOT use iSpot to identify fungi to eat!
Some fungi are very poisonous so a mistaken ID could have serious consequences.
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Have I understood correctly, this is the same organism but now with a different name?
Thanks for your help and suggestions on what to look out for. I will take out a hand lense and have a closer look at it. I have a second picture of another rock with what seems to me to be the same lichen on it, if it helps. Can it be added to this observation or must it be a new one?
Having discovered that I can indeed add another photo, I've added another picture, not quite as sharp as it might be, but maybe enough to be sure that it isn't actually tar!
I am always a bit twitchy when folks add photographs after an identification has been made. I have suggested to iSpot that photographs added after an ID should have their date of addition clearly marked, but was totally ignored of course.
In this case, photo 2 looks more like actual tar than photo 1!
But if we assume it's lichen, then to confirm, it is Verrucaria amphibia (now more correctly called Hydropunctaria amphibia). I think.
Verrucaria maura (= Hydropunctaria maura) is a different species, generally has a thicker, cracked thallus, and grows a little higher on the shore.
There are other black Verrucaria (Hydropunctaria) species as well. They need microscopic examination of sections.
Lat/Lng: 57.69639, -2.8056
OS grid ref: NJ520676
Below high tide level in the area known as the Salmon Bothy Bay.