White Cocoon with an opening?

[kssalah]

This is on the same rock as the pink sponge thing. It's about an inch around, and sticks up about 1/2 an inch high. It has an opening. There is actually two of these things on the same rock. Any idea what it may be? The rock also has a bunch of mushrooms on it. The reason I am trying to figure out what the things on the rock is, is because the mushrooms on this rock don't open as big as all my other mushrooms. Is this guy good or bad for the tank?
thanks again for all your help!

 

[whisk]

i dont know what im suppose to be looking at, anyway you can circle it or get a clearer shot?

 

[kingsmith]

Sounds like it might be a sponge but I cann't see any pics at work

 

[reefreak29]

looks like a sponge

 

[zman1]

taste like a sponge

 

[funkysean5]

Yep, sponge.