Confidence: I'm as sure as I can be.
Notes: Contrary to the notes above, this does NOT appear to be sorediate over the entire surface of the thallus. It is warty but smooth, like hardened porridge, and also it lacks the fimbriate margin of Haematomma. Usually O. ventosa is yellowish, but like H. ochroleucum it has a grey variety lacking usnic acid, var. subfestiva, and this is what we see here. In my experience it fruits much more commonly tham Haematomma.