Notes:
At first I thought this was a Volvariella, then I noticed it didn’t have a volva. It had free gills and the older specimen’s gills were starting to turn pink, so I concluded it was a Pluteus. However, when I got home and tried to look it up, I realized that Pluteus doesn’t normally have a ring. Arora makes a comment about the genus Chamaeota as a genus in the Pluteaceae that has no volva, but does have a ring. None of the other books I checked even mentioned the genus. Looking on the web I found a photograph of Chamaeota sphaerospora on MushroomExpert.Com, but no other photos.

However, when Darvin looked at it he suggested that it might just be Leucoagaricus leucothites. This seems pretty likely. I put the specimen on the drier before I took an actual sporeprint.

I also check a couple of microscopic feature based on an email from Else Vellinga. The spores definitely had a germ pore and the gill trama did not appear to be convergent as it would be for Chamaeota.