Tudorella melitense (Sowerby, 1847) is the only snail with an operculum ('door') which is native to the Maltese Islands. Under a 'biological species definition' it may be considered to be a local variety of Tudorella sulcata (Draparnaud, 1805), which also occurs in Sicily; Pfenninger et al. (2010)*, in their work on the DNA of Tudorella, consider it a lineage which is only found in the Maltese Islands.
*Pfenninger, M., Véla, E., Jesse, R., Arantzazu Elejalde, M., Liberto, F., Magnin, F., Martínez-Ortí, A., 2010. Temporal speciation pattern in the western Mediterranean genus Tudorella P. Fischer, 1885 (Gastropoda, Pomatiidae) supports the Tyrrhenian vicariance hypothesis. Molecular Phylogenetics and Evolution, 54: 427-436.