A shellfish of some description

[Streetlamp]

Anyone know what this is. I occasionally spot an empty shell around the place. Today I found a closed one.

 

[P-Dub]

That is the operculum or the snail's trap door.

 

[Streetlamp]

Oh that’s a little disappointing. Thought it was something more interesting

 

[Soren]

@Streetlamp I've got a few of these in my reef from large turbo snails that were lost by the previous owner of my 75-gallon FOWLR. The shells and operculums are both left, and I was surprised with the first discovery of the loose operculums as well until I made the connection.

Yours looks like it is from a different species, though.