Here is a shell of Batillaria minima with its inside exposed. It took me a while to remove the ventral side of the shell carefully with a small file.
The apexes of the shells of adult and most juvenile B. minima are normally eroded. Notice that the uppermost 3 whorls of this specimen are filled with shell material. The snail probably did that to strengthen the apex against further damage and also to prevent its body from getting exposed in case of additional breakage.