There are a dizzying variety of mushrooms; so much so, in fact, that I'm hard pressed even with a field guide to identify most. This one is no exception. Looks to me like Lepiota procure. Can anyone confirm that?
Lepiota is a genus of gilled mushrooms in the family Agaricaceae. All Lepiota species are ground-dwelling saprotrophs with a preference for rich, calcareous soils. Basidiocarps (fruit bodies) are agaricoid with whitish spores, typically with scaly caps and a ring on the stipe. Around 400 species of Lepiota are currently recognized worldwide. Many species are poisonous, some lethally so." -- Wikipedia