Hypsizygus ulmarius

Hypsizygus ulmarius, also known as the elm oyster mushroom, and less commonly as the elm leech. It has often been confused with oyster mushrooms in the Pleurotus genus but can be differentiated easily as the gills are either not decurrent or not deeply decurrent. While not quite as common as true oyster mushrooms, they have a wide range globally in temperate forests. It is an edible species. The mushrooms and vegetative hyphae of this species have been studied in recent years for their potential benefits to human health, and mycoremediation....read more on Wikipedia.