ID my sea monster?

[twistedenvy]

Hey Guys,
New hobbyist here, and it looks like I have a hitchhiker on my rock. I have had this rock for about2.5 months now, and have been constantly looking at this thing. It almost NEVER moves,and therefore I thought (but suspiciously) it was just some odd shaped rock or something.
Yesterday, my goby went up and just stared at it while I was watching, and the thing MOVED! So like the dork I am, I went running through the house to grab my boyfriend and make him see it to so I knew I was just seeing nothing. Sure enough, it moved again. I have now discovered that if I poke it (not with my hand eek!), it recludes back into the rock as far as it can for about 10 seconds. You can see that it closes its mouth if i poke it. Help??

 

[cranberry]

Could it be a boring (as in drilling... not *yawn*) clam? Or at the least a bivalve of sorts.

 

[twistedenvy]

I am agreeing with the clam idea a lot more than the starfish theory from WRS. They are now going with clam too. Only thing is that nothing ever comes out of it, and when it closes, it just closes its mouth and shrinks for like 5-10 seconds. I'm a newb, but I searched the internet and doesn't look like any of the boring clams or bivalves that i saw.

 

[cranberry]

The side to the left totally looks like a bivalve... I have just never seen the hook type part to the right.
It's the part to the left that opens and closes, right?

 

[flower]

I can see why you didn't notice it at first LOL.
I had the same kind of thing on one of my rocks that had coral. It is some sort of clam. Mine didn't live very long...about two months then it stopped moving and became part of the rock.

 

[twistedenvy]

That is what I thought at first; just something that was part of the rock. Now it has come to life and moves sort of easily now. Thanks everyone!