Herman Henstenburgh made this drawing, which is now in the collection of the Fitzwilliam Museum, Cambridge . In their catalogue the tile is “Flowers entwining a vase which stands on a ledge with snails and insects”. Although slightly more abstract formulated, this seems more accurate than the title in the RKD database (“Still life of flowers draped around a vase with damaged edge, a sheet and two snails on the corner of a stone plinth”) simply because there are more than two snails in this drawing.
In the lower left, indeed two snails can be seen at the corner of the stone plinth.
However, a third snail is visible in the central part. For sure, this specimen is less clearly visible in the low-resolution black and white copy available at the RKD .
All three snails are dextral specimens of a Cepaea species.
 FWC, inv. PD.645-1973. http://data.fitzmuseum.cam.ac.uk/id/object/23558.