Another ID Please!

[Der_Iron_Chef]

I noticed two strange looking things on the piece of live rock my green hairy mushroom coral came on. They open and close, like mouths, and seem to go into the rock. The area immediately surrounding them looks like a dried prune, for lack of a better description. Two pictures to follow: picture one is at night, and the "mouth" is partially closed; picture two is during the day and the "mouth" is fully open.

Any ideas?

http://x02.xanga.com/d27a81f71113091011856/w63215822.jpg

http://x41.xanga.com/fcbd12e44873391011867/w63215833.jpg

[Tarolisol]

Judgeing from the first picture, id says it one of those creatures from tremors. But looking at the second i would say a sea squirt.