What is it???

Hello everyone,
I do not have a picture of it just yet, but wanted to go ahead and ask to see if anyone is familiar with what I noticed attached to my live rock last night. It was probably 3/4-1/2 inch in height about 3-4cm wide...was white and oval in shape, positioned vertically on the underside of the live rock piece. It almost looked as if it had a sprouting of a small feather duster head (its not a feather duster, but small wispy frons in a circular motion at the top, very small, almost cant see them.)

Ill try to post a pic later, but does anyone know what it could be from my description? I'm more prone to saying its some form of plant, or coral...not a snail/slug type animal, but wanted to know if anyone has any incite as to what it could be.

Thanks a bunch for your help.

 

Foraminiferans?

http://www.reefs.org/hhfaq/pages/picture_pages/faq_foramwhite.html

http://www.reefs.org/hhfaq/pages/main_pages/faq_rock3.htm

 

Thanks for the links...okay, I'm thinking it might be a sea squirt. Based on some of the pictures I found online. Is it possible that it could have come in from some newly purchased Zoo's I bought? It is on a very small piece of rock, all the way on the other side of the tank from where the zoo's are placed. Hmmm...interesting! I love how things just appear...large enough where you cant understand how you didn't notice them earlier, seeing as though I stare at my tank hours on end! Ill still post a pic of it when I get home. Thanks again!