Here is the underside of the previous picture of the caps. Note the fuzzy white base, thin stem (hollow), buff crowded gills, chocolate brown spore prints.
log at Prospect Park
there are fragments along the margins of the caps. Does that make it a Psathyrella or Panaeolus? Do they grow out of logs? It's also hard to say what kind of brown the spores are, they're very dark brown, like a dark-chocolate bar, but could it also be purple-brown? Don't know.