From RebeccaAlexa.com: How to identify late oyster mushrooms.
Young late oyster mushrooms may have edges that roll under, but when mature they open to a flatter shape, sometimes with a gently scalloped edge. The stipe is quite unique with its fuzzy texture, and is generally very short. The tightly-packed gills are adnate, meaning that they attach to the stipe with their entire width, rather than becoming shorter in height as they approach the stipe. Take a spore print of a late oyster mushroom, and you’ll find a cream to yellow print. The flesh does not bruise or otherwise discolor when damaged. [continue]