FOUND IN CROATIA
In 2013, scientists discovered a new species of an unusual cave-dwelling snail in Lukina Jama–Trojama in Croatia, one of the deepest cave systems in the world.
These tiny and fragile snails, classified as Zospeum tholussum, have a beautiful dome-like translucent shell. They are a part of a genus of minute air-breathing land snails that are exclusive cave-dwellers.
Remarkably, only one specimen of this new species of snail was found when it was initially discovered. The snail was resting 980m (3,200 feet) below ground, deep inside the cave system in a little cavity full of rocks and sand with a small stream running through it. The miniature snail doesn’t have visual orientation as there's no light that far below the earth's surface.
Clancy's comment: Only one found!