The Oyster Mushroom Pleurotus ostreatus
This group was on a Rowan tree.
The species is of variable colour, including brown grey and white.
This one (third image) seems to have had its gills chewed by slugs.
The stereos are crosseye.
Olympus EM-1, (aperture priority), Olympus 4/3 50mm f2 macro, 1/100 and 1/200 at f8 ISO 3200, hand-held.