Opinions Anyone?

[Jeff D]

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?

[david touitou]

Hello, 

The problem is that these shells have crusted algae or coral on them and we cannot see the "real shell" under this crust...

DAVID

[Jeff D]

That never crossed my mind, but makes perfect sense....can't thank you enough for the feedback.

[david touitou]

No problem, sorry I can't help you more...
 DAVID

[Jeff D]

No worries....in the next day or so, I may have one or two more puzzlers. Your help would be greatly appreciated. Thanks again.

[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

[Bence Cs.]

Oh and one more question:
was its entire body in the water?
If it was, it's possible that it's a Porifera (sponge) species rather than a sea urchin.

[Jeff D]

Pried if off the rock and it definitely had a slug inside....it had a hard shell exterior and there were some both above and below the water line, as the tides came in and receded.

[paul monfils]

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?

Given the general shape, size, and habitat, these most likely belong to either the Family Trochidae, or the family Littorinidae.  There are several species from each family which live in this kind of habitat, in this geographical area.  If you brought any of these home, you could soak one in bleach solution and perhaps remove enough encrustation to reveal some details of its structure, color, etc.

[Jeff D]

That is something that I might do, although I really do like the current colour it has.... I really appreciate you narrowing it down for me Paul. Thanks again.