It is found in presumablly upper Eocen-lower Oligocene clay sediments in SW Bulgaria. Given the size of the fossil and the facies feature of the sediments I think that, it belongs to the Hydrobiidae family.
Article The genus Diplommatina Benson, 1849 (Gastropoda: Caenogastro...
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I hope above links might be helpful. Thank you!
Maybe is fossil species of Landshells belonging to the group of Zebrina.
Do you at least have an idea is this species marine or terrestrial?
If terrestrial, my first suggestion would be Enidae or Achatinidae but both are very speculative. And, of course, how big is your specimen? Any measurements available?
Dear Dmitry,
You can see the size of the specimen on the attached picture.
The fossil site is very poor. I have found only two species of gastropods.
The big one which so far was determined once as Cepatia cetacea - Naticidae and once as terrestrial helicoid (Helicidae, Elonidae or a similar family) I am attaching pictures bellow.
The site does not contain fossils of bivalves which is unusual if the sediments are marine.
The second gastropod is the small one from my question.
A colleague from Germany thinks that it "might belong to the family Enidae"
The fossil layer is built of white to grey coloured chalky -tuff sandstone that is deposited between green clay layers.
Bets regards: Miroslav