This is a Monacha syriaca shell—one of the specimens we collected last summer in Turkey. Its aperture is almost perfectly sealed by its calcerous epiphragm. What appears to be a hole at the bottom doesn't open to the inside of the shell. There is only a very narrow, short gap, visible at the top corner of the epiphragm, that the snail may have left open for air exchange, although I am not sure if it goes all the way thru the epiphragm to the other side.
The snail was obviously ready for the long, hot, dry Mediterranean summer.
But, the shell is empty; there is no snail in it. When it is backlit, the light shines thru the shell, except at the apex where there is some dark matter. And there is no hole anywhere in the shell.
The snail died, decomposed and dried up. It couldn't survive the heat or the lack of water or something else. Its sealed home became its sealed coffin.