What is this?

[mot ii]

We are in the process of upgrading from a 65 gal to a 90 gal, and as we were taking out the live rock we found these odd circular ball type things on the bottom of one of the pieces of live rock. We don't know how long they've been there (we've had the tank going since 2007) nor what they might be. They look like they are of a slimy type consistency. Any thoughts??

Thanks!

 

[monkey tang]

Looks like some small sponges to me, I have them in spots on my rock as well