https://pubmed.ncbi.nlm.nih.gov/31716572/
Operculum shape variation in Theodoxus Montfort, 1810 (Gastropoda: Neritidae)
The operculum morphology of neritid snails of genus Theodoxus Montfort, 1810 yields important species-specific taxonomic characters. This study is the first...
shapevariationmontfortgastropodaneritidae
https://species.wikimedia.org/wiki/Neritidae
Neritidae - Wikispecies
neritidaewikispecies