Can You Identify These seashell (fossil)?

[paul monfils]

These are not fossils. This is Magilus antiquatus, a strange species in the family Coralliophilidae, which bores in coral.  The juvenile shell looks like a typical little snail, as in the upper image; but as it grows it loses its spiral form and takes the form of a heavy tube, as in the lower image.  Also, as it grows, it completely fills in the interior of the shell with shell material, first the spiral portion, and then successive portions of the tubular part, which is why they look like fossils.