Under a rock. Empty shells. Width approx. 3 mm. Its spire is too flat to be Zonitoides nitidus, the last whorl seems too expanded to be Z. arboreus. Its umbilicus seems too large to be Oxychilus cellarius, and its growth lines are stronger. More sculpture on apical than umbilical side.
Very very small
In a dark space between high rocks
Crawl around
Shell looks like it has ridges
Crawl slower than the hermit crab