Any idea what this is?

[scubachris]

Ok about 2 months ago I bought a piece of LR with 2 green hairy mushrooms on it. I noticed about a week later all of the feather dusters that came out of the rock, but just recently saw something new. On the back side of the rock there is what looks like a clam. It has a green clam like shell, and when it opens up what looks like a deep blue feather duster comes out. It is about the size of a pencil eraser when closed and slightly larger when opened. I cant get a pic b/c of where it is. Any ideas?

 

[keri]

Google "barnacle" the inner part of the shell resembles an oyster a bit and a feathery bit comes out to feed. I've seen blue ones.

 

[smokingreefer]

+1 on barnacle