Opinions Anyone?

[Bence Cs.]

I found a group of these shells (with slugs inside), nestled among chitons in a rocky tidal zone area at the Barcelo Maya in Mexico. Can anyone help?

Hello,

I'm not sure, but I think this isn't the shell of a Gastropoda (snail) or a Bivalve (clam) species.
I think it's an external "skeleton" from the phylum Echinodermata (echinoderm) and class Echinoidea (sea urchin)
Have you seen a hole (its mouth) on the "belly" of the animal?

I hope I helped,
Bence