I couldn't get a good picture because it's too small. It's about a 1/4 inch and all white except for it's 2 brown horns/antennas. It hasn't been hanging out by my zoa's it particular that I've noticed. It has been crawling all over my LR.
Actually it hasn't lost its shell.. It's still there, it's just very small and only covers part of its body.
They are good guys. If yours is only a quarter inch, the it is a baby and you likely have more and they are breeding in your tank
The differences between this and the stomatella are that this guy doesn't seem to have a shell (even a little one ) and his horns are more pointed kind of like a devil as apposed to stringy antennas like snails have.
Your little guy is too skinny to be a stomatella. My stomatellas multiply all the time and they are wider than this guy.
He might be a marine worm (there are about 6,000 different types), but either way he doesn't look like something I'd worry about.
You're not seeing any issues in the tank?
How much is it worth to you? If its something without a identity and i have expensive corals in my tank i would either A--Put it in the sump B--In the garbage. Why take a chance