Good-sized mushroom. Underside and stem of mystery mushroom #1. It was just completely white underneath, white gills, white stem, with pale grey-brown cap (see cap pic #1 of 2), with white spores. The stem was really fibrous, really stringy when pulled apart. Somewhat tough.
Pushing through leaf litter on forest floor, blue trail of Staten Island greenbelt.
Took home to do spore print and it was white.