That's a pretty good sized 'shroom! I am not sure of the species, although I have seen these around here as well before. Maybe take google and take the pic and see what it comes up with. I tried it with my app plantsnap, but the 'shroom it brings up isn't the same. Let me know if you find out. I've seen these as big as around 8-10" before. I just call them pancake 'shrooms! Take care sis! !LUV