Snail's shells empty and slim covered...?

[OceanicCorals-Ian-]

I had a huge Polyclad Flatworm that ate snails and actually ate a small Clam in my old tank. The beast was completely nocturnal and only ate snails, I caught it one night dragging a snail into a hole.

I identified the Flatworm as the one that I have linked below;

http://www.seaslugforum.net/display.cfm?id=16272