|I’d Call It That||3.0||5.46||1||(jason)|
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It’s the white speckling all over the surface. This is ambiguous in the British Flora: ssp. islandica has distinct laminal pseudocyphellae like yours has, but is supposed to have flattened, broad branches; yours has “subtubular” narrow branches that look just like the typical ssp. crispiformis in North America. Certainly, there is no question this is C. islandica and not C. ericetorum, though (its pseudocyphellae form lines along or just back from the margins underneath the branches).