Help with ID - Is this a clam?

[-Pixie-]

Hi everyone - Just wondering if anyone could please tell me if this is a clam (my partner thinks so) or if it's anything at all?

Also does the light blue thing under it look like a sponge?

 

[jenjen]

The bluu-ish thing looks like a sponge, but I don't see anything that looks like a clam. Sometimes on live rock you'll see little mussels or other tiny filter-feeders. Could be you're seeing one of those?

 

[-Pixie-]

Thanks

 

[Frick-n-Frags]

i cant really see a clam. i see several different sponges and macros.

sometimes oysters will grow embedded in LR. they have a very irregular mouth and are quite well disguised. you can usually only notice they are there when they are open.
mussels come in on LR too. they are generally standard mussel shaped.