Vallonia adela Westerlund, 1881 Vallonia declivis is a species of very small air-breathing land snail, a terrestrial pulmonate gastropod mollusk in the family Valloniidae.

This species is found in Austria, France, Germany, Poland, and Switzerland.

[1] It was previously listed as part of the fauna of Slovakia, but Čejka considered its occurrence in Slovakia unlikely.

[4] It lives also in the Czech Republic (in Bohemia only) and in Slovakia.

This Valloniidae-related article is a stub.