What is growing in my live rock?

[hubbcass08]

I just re-arranged my live rock and found this little guy inside a crevice. It seems to be pretty well attached in there. I have no idea what it could be. Its an off white color, it opens like a clam or oyster would but closes if you shine light on it. Any suggestions? The texture reminds me of a mushroom but I'm afraid to touch since I don't know what it is. The very bottom photo shows it opened a little bit.

 

[nirbhao]

I'm curious!

 

[Sniperhank]

Looks like an anemone of some type.