Psathyrella, I think.
Heavy rain all day.
On the left, a side shot showing the wide (4cm.) cap and the shiny white stem (stipe). On the right, the underside, showing the gills.
This is the spore print on glass. Millions of spores have been deposited in 24 hours.
On the left, spores at x100, showing the 'banded' appearance of the print. This is caused by the spores falling unevenly from between the gills. The right hand image (x400) shows that the spores are individually brown , smooth and oval.
