Great close up. In France, we call this mushroom a coprin and it is pretty common here, but I do not know the proper English word for it. The black part indicates that this one is already too old to be eaten; when it was younger, it was all white and it should have been edible. But do not take my word for it, I am not an expert :-)
I think it is the same mushroom that I have posted here, in an even older state : https://365project.org/etienne/365/2019-10-19