LR hitchhicker, any ideas?

[Ohio]

Yellow, started out flat on rock and now it appears to be growing polyps. Is it a type of coral or sponge? Thank you for taking the time to help me ID this:

http://www.reefcentral.com/forums/picture.php?albumid=2922&pictureid=20520

http://www.reefcentral.com/forums/picture.php?albumid=2922&pictureid=20519

[2Addicted]

Is it hard? Do the polyps retract when you disturb it?

[Saltfinsax]

I wil take a guess and say a yellow leather.

[canesfan44]

those look like polyps. I agree with above, do the polyps retact?

[2Addicted]

Looks like some sort of monti. If its hard that would be my guess.

[Ohio]

Not sure if it is hard, I can check though. The polyps do retract after lights out.

[Ohio]

Thank you all for the responses

[Supasalty]

It looks like a yellow toadstool to me. Some one could of removed one but left a tiny bit that has started to grow.

[mallorieGgator]

awesome hitchhiker!