Any ideas what this invert could be?

[lyscer]

I found this guy in my overflow about 6 months ago. Hasn't moved from what I can tell but has gotten much larger. (Not the bristle worm but the mollusk type thing.

I know it is a long shot on identification without a shot of the shell but am curious as to what it could be. I can't get a shot of the shell as it is in too tight of a place.

 

[Lionfish Lair]

As you suspected, we really do need to see the other side. It could be a limpet.

That worm is a Dorvilleidae, BTW. :)

 

[lyscer]

Here is a partial shot of the shell I got tonight by scraping the glass in the overflow.

 

[kashman100]

Stomatella snail maybe