What is this on my rock?

[shoelaceike]

Looks like some kind of anemone. They are small, only seem to open at night and are yellow when closed.

 

[EeyoreIsMySpiritAnimal]

Ball anemone - corallimorph

 

[Jekyl]

Ball anemone

 

[EeyoreIsMySpiritAnimal]

Looks like some kind of anemone. They are small, only seem to open at night and are yellow when closed.

And it's actually not an anemone, despite its common name. It's a mushroom.

 

[shoelaceike]

Thanks!