This is Zonitoides arboreus, common name Quick Gloss. I found many of these tiny snails at Frances Slocum State Park on the mountain bike path the same day I found my Philomycus togatus. I've just been lazy/busy on making an identification. Actually it's two individuals I found at Ricketts Glenn that have been consuming the time I have to study identification-- and I still haven't id'd them.
Anyhow, click on the photos to enlarge. The two colors are pretty cool-- dark up top, clearish down bottom.
Range map from Land Snails of Limestone Communities and Update of Land Snail Distributions in Pennsylvania (Pearce)