Very strange creature living in half a clam shell

[linty]

I got a piece of live rock (polynesian I think) and there is a half clam shell pretty much part of it.  The half clam shell is about 3 inches across it's widest point.  Now, in the bottom part (where it forms a sort of small cup) there is a weird little beast living there.  I don't think it was there when I first got the rock either, although I could be wrong.  At first I mistook it for just debris, but it reacts to movement nearby.

 

It is about 3/4" in diameter and it's shaped sort of like the smart blade in the predator movies...er...like a circle with two notches in it.  it's not very colorful, and it has no filtering appendages that I've seen so far.  It looks like the round visible part is tough, an operculum or something.  I can try to take a picture but I don't know if it will work because the angle is very awkward.

 

I'd appreciate any guesses as to what it may be.

[MarkF]

Tough without a picture.  I guess Chicid, it is kind like a cross between a snail and armadillo.  They're good to have around.

 

Hope that helps

Mark F

[linty]

No, I don't think it is a chiton.  It seems adapted to living in depressions, it doesn't seem to move away from where it is.  The only movement it makes is moving deeper into it's crevice when it is startled, and it moves quite fast.  

[linty]

here are some pics of it (sorry, they are blurry)

 

[Cam barr]

have no  clue but you could sipion it out

[linty]

it seems to have a good grip, and I don't want to hurt it if I don't have to.

[dawn]

i could be a limpid(like a tiny clam) i had some on some of my live rock

 

little hairy looking with colored inside when it opens

 

they attach to anything they like and can bury them selfs in the sand to

 

good luck

[linty]

i'm pretty sure it's not that either