Shell or Coral

[billham]

I can't find a starting place for this one, I am pretty sure it is a shell, looking in opening of central spiral. Found in the Florida Panhandle, Northern Gulf of Mexico.  Hard corals are very limited here.

[paul monfils]

I can't see an image if you posted one, but there are several species of hard bryozoans (microscopic colonial animals unrelated to corals) that frequently encrust small shells.  The aperture of the shell is usually visible, and may even be inhabited by a hermit crab, but the bryozoan colony may take on a very different shape from the original shape of the shell, often with spikes sticking out in various directions - or in just two directions, as in this one:

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[billham]

Thanks... Mystery solved both shell and coral.  A Texas Longhorn who knew?  A great addition to my collection.