This marine snail shell was from a small sample of sediment that I had collected while snorkeling off the southwestern coast of Turkey back in 1997. Only recently did I begin to sort thru the sample (yes, I am that far behind). Henk Mienis of Tel Aviv University identified it from the picture as Ammonicera fischeriana.
With a diameter of 0.6 mm, it is the smallest marine gastropod I have so far seen. Apparently, they only grow to be about 1 mm or so. Ammonicera fischeriana is in the Omalogyridae, a family of very small snails. This being my 1st encounter with them, my knowledge of the family is quite limited. Hopefully, there will be more opportunities to study them in the future.