Crowded White Clitocybe

Clitocybe dilatata

Large, clustered, overlapping, fleshy, white mushroom with wavy, lobed to split margin.
Clitocybe dilatata Clitocybe dilatata - pretty sure that's what this guy is. It occurs here and other examples have been found in the same general area. 
http://mushroomobserver.org/name/show_name/1765
http://www.rogersmushrooms.com/gallery/DisplayBlock~bid~5789~source~gallerychooserresult.asp Clitocybe dilatata,Crowded White Clitocybe,Geotagged,United States

Appearance

Cap: 2-6" (5-15 cm) wide; convex, becoming flat; margin incurved, becoming irregular and upturned; dry, smooth, whitish. Taste disagreeable.

Gills: attached or slightly descending stalk, close, narrow;, whitish to buff.

Stalk: 2-5" (5-12.5 cm) long, 1/4-3/4" (0.5-2 cm) thick; dry, fibrous, white.

Spores: 4.5-6.5 X 3-3.5 m; elliptical, smooth, colorless, nonamyloid. Spore print white.

Naming

Also known as C. cerussata var. difformis.

Uses

Edibility: Poisonous.

References:

Some text fragments are auto parsed from Wikipedia.

http://www.herbmuseum.ca/content/clitocybe-dilatata-crowded-white-clitocybe
Taxonomy
KingdomFungi
DivisionBasidiomycota
ClassAgaricomycetes
OrderAgaricales
FamilyTricholomataceae
GenusClitocybe
SpeciesClitocybe dilatata