I found this mushroom while hiking in Lynn Valley, on a log fairly close to the river. It was pure white, with a sort of involute cap with a crenate margin. The cap was smooth and slightly velvety, and there was no visible partial veil or stem. The gills were long decurrent and fairly narrow, with even edges. I think this is an Angel Wings mushroom, Pleurocybella porrigens, because it looks very similar and has the same features.