Вероятно, мы нашли категорию простейших по вашему запросу:

Genus Trachelocorythion

Main body of the shell is covered by scales of regular size and shape; flattened cross section. The upper lip of the aperture larger than the lower resulting in a slightly subterminal opening, no collar. Ecology: dry soils to forest litter and Sphagnum mosses. Monospecific. Type species: Trachelocorythion pulchellum (Penard, 1890) Bonnet, 1979