what type of coral do you think this is?

[threebuoys]

I noticed this behind a rock and in a corner at the back of my aquarium. The only thing I can think of is a mushroom, but I never seen one with a long, thick stem. The top is partially closed now. When I first saw it, it looked like a megaphone or similar to a morning glory flower. The top is blue, and the stem is a translucent tan/beige color. The stem is about 2 inches long. and the top has a wide spread when not retracted. I do have a lot of mushrooms which are propagating like crazy.

Thanks

 

[crazyfishmom]

Looks like some sort of leather to me. Pretty neat!