Earlier this year my sister found this gorgeous, translucent, ethereal mushroom with yellow "umbrella ribs." She asked me to identify it for her, and I believe it is Pleated Inky Cap. The scientific name was listed as both Coprinus plicatilis and Parasola plicatilis.
this is the most beautiful mushroom I have ever seen. Since they are her photos, I am just posting a link to them.