What is "bythinella"

Bythinella is a genus of very small freshwater snails, an aquatic gastropod mollusk in the family Amnicolidae (according to the taxonomy of the Gastropoda by Bouchet & Rocroi, 2005).

These gonochoristic snails are small animals, with a shell length of about 2–4 mm. Amnicola is a close relative, containing North American snails with essentially similar appearance and ecology. The scientific name means "small Bithynia"; the latter snail genus is somewhat similar at a casual glance (though much larger) but not at all closely related among the Rissooidea.