Looks to me like what we called the Rams Head/Sheeps Head back in Pennsylvania. Also called Hen o' The Woods out here in Missouri. Stores and health food places call them Maitake. They vary a lot but I just posted pics here recently of one that I picked in my yard. Look for a thread about "OMG 20+ pound mushroom" or something like that. Also, do a google search on those names and look closely because mushrooms are a bit tricky to ID sometimes. The one I'm talking about does not have "fins" on the bottom side and they can get quite large. Up to about 2.5 feet across. Mine this year was just over 8 pounds. If it's the type I'm talking about, they are delicious but the one in your pic looks like it's getting old already.