Hitchhiker IDs

[amanda_marie]

I just added another 10lbs of live rock to my tank that just finished curing. So far these are two hitchhikers I've found, I never really had any on any of my other live rock.

I've circled the two items in this picture. I've pretty sure the top is a sponge. The other looks like a clam/scallop/or similar, I'm just not sure. Whatever it is, how do I know if its actually alive?

I'm assuming both are harmless though.

Thanks!