Need help with shell and coral ID

[hma]

Hi buddies,

need help to identification this shell. Can't ID them 100%, maybe someone here on RS has any idea? Maybe some kind of ouster?

Under the shell, at the lower edge of peel grows an even small coral (1,5cm slowly growing over some weeks), what could it be? I have a guess, but would first wait for your answers before I call my suspicions.

By the way .... this little thing is NO ASTERINA, I know it looks very much like an asterina but it is def a coral but which one?

Thanks

 

[aaromano]

I agree with you looks like some type of oyster. Maybe some type of porites coral?

 

[Reefmack]

Strange coral. It almost has double arms that vaguely resemble those of an asterina, yet doesn't look like an asterina, and doesn't appear to move. Weird!

Heinz - can you tell if those are individual polyps on the surface of the mystery object?