It is kind of hard to discribe. It doesnt have any tenticles that come out. It is attached to a rock at the base, It is not encrusting like a chalice, but is more like a mycedium. Almost like like a plate. I will try and get better pics from the side.
I saw something like that in St. Maarten... I didn't remember there being any chalices in the Caribbean, but when I saw that one (saw two different pieces on different dives), I was drawn to it. I knew I'd seen a picture somewhere before...