ID please..

[NanoReefWanabe]

well i have no idea what this is or where to post it...but here it is can anyone ID it...

the round disc like thing in the centre of the pic...

here is a pic of it open...

and here it is after i shone a light on it and it snapped shut..and sucked into the trock about 1/8"..

 

[clayspst]

its a rock

 

[ManEatingGuppy]

looks like a hitch hiker clam

 

[LeslieH]

I agree, it's a rock-boring clam. They're all filter feeders.

 

[NanoReefWanabe]

thankyou...he is nothing to worry about then?

 

[LeslieH]

Nope. Just a harmless little guy helping to keep your tank clean by filtering particulates out of the water.