One can find in Loën quarry 5 Clausiliidae snails. But what are Clausiliidae ?
They are snails with an elongated shell making a pointed shape, sometimes covered by axial ribs.
Another feature : they are sinistral, meaning that their aperture is on the left side of the shell when handling it with the top above. Inside this aperture, one can find various folds and strips that are useful to determine the species.
The name of this snail's family is derived from the "clausilium", a movable plate located deep inside the aperture. When the animal goes out of its shell, the plate is moved on the side and when it withdraws into its shell, the clausilium returns on its initial position.
To identify a Clausiliid shell for sure, you will need to examine, among other features, the folds and strips located in the aperture. But even without these hints (difficult to use with a living specimen !), you can apply some rules to assert the name of the Loën quarry species you are handling :
1) shell small (< 12 mm) and smooth : Clausilia parvula;
2) shell medium (between 12 and 14 mm) : if the shell is paunchy with a weak basal groove on the aperture, this is Macrogastra rolphii, otherwise it is Clausilia bidentata;
3) shell bigger (> 14 mm) : if the shell is smooth, this is Cochlodina laminata, if it is stripped, this is Macrogastra attenuata lineolata.
To be sure that the shell you are examining is adult, remember that only the adults specimens have a full developed aperture.