These suckers really confused me when I found them. Rhodocollybia crossed my mind, however the over-mature specimens looked very unusual to me, with the cracked pileus, and especially in the cespitose clusters. There were two almost identical clusters of comparable age within a few feet of each other. I looked around the area for some fresher specimens and located 4 VERY young mushrooms within a yard from the other two clusters. At least I am pretty certain that they are a younger version of the same thing.