Lepiota helveola

Lepiota helveola is a gilled mushroom of the genus "Lepiota" in the order Agaricales. It was described by Italian mycologist Giacomo Bresadola in 1882.
It has white gills and spores. They typically have rings on the stems, 
Like several other species of the genus "Lepiota", it contains amatoxins which may cause potentially fatal liver injury.