strange growth on my turbo

[sansouci01]

One of my turbo snails died. I just left the empty shell in the tank for my hermits. It's kind of hidden near my rocks so I haven't paid much attention to it until today. I noticed a strange growth on it. It's on most of the shell. Anyone know what it is?

 

[Mebbid]

Looks like its a polychaete of some sort. Also, that's an astrea shell

 

[chefbill]

The growth looks like vermetid snail.