I spent the evening tonight leafing through plant and lichen books, browsing Google photos, going through alphabetical lists of lichen from A to Z. (E-Flora BC tells me that the UBC Herbarium Lichen Database has 35,000 records. I'm probably fortunate that their page wouldn't load.)
And I am no further ahead than when I started.
I saw this leaf lichen this afternoon. Pretty, I thought, and snapped the photo.
Greyish white, lobed, loosely attached. So far, so good. I see lichen like this in every clump of trees.
But I haven't been looking closely enough. This afternoon, sorting my photos, I noticed the underside of the lobes. They are covered in little dark brown teeth or spines.
Enlarged photo; you can see the jagged underside. Click on the photo to get a better view.
So I've been searching. I don't know what this is. It could be some type of Nephroma; at least that is the closest I could find. But nothing quite matches.
And I never imagined there were so very many species of lichen.