Siamese Twin?

[75Gallons]

I have pretty large mexican turbo snail that has some sort of calcified shell attached to it. The thing inside of the shell is snail like in appearance and shoots webs out of its mouth and then pulls the webs back in after awhile. Anyone have any idea what it is? Im having problems with my camera right now but i'll get pics as soon as i can.

 

[gtriamy]

medusa worm? i think thats what they're called, i see em all the time at the LFS on the live rock and such. few long tenticles, no coloration? i'm pretty sure they're safe. maybe Chaetopterid? check melev's site.

 

[BethanyM]

vermetid snail, unsure of exact spelling.