This is one tiny snail which I never even knew existed until the other week. The shell grows no longer than 4.4mm (0.2in) long. Note it has only one single tooth in the shell opening (see image below), which helps identify this species, and also it is quite a plumpish looking snail with 5 to 6 whorls and a blunt spire compared to other similar species. The snail itself is fairly dark with pale sides.
They are Ovoviviparous, which means the eggs hatch within the body of the animal, and then they give birth to live young. They can live up to 4 years. Quite common and widespread throughout woods, damp grassland and gardens. It can be seen all year round.
July 2017, rear garden, Staffordshire, England.