What is this and why is it doing that

[mstr.limpet]

I bought this thing from a lfs about a month ago because I wanted the pulsating xenia's. The question I have is what is the thing they're attached to? When I first got it it had smooth edges, now the edges look jagged. Is this normal or is there an issue? Thanks for the help.

 

[Diverdown1]

Looks like an upside down chalice coral(LPS)

 

[mstr.limpet]

Please excuse my ignorance, but is it physically upside down or is that the name.

 

[mstr.limpet]

I turned over the chalice, and the opposite side is white with a lot of spines/spikes. The side I had facing up is kind of a light purple. I think the light purple side should be facing the lights. It almost looks like the new rough edges are the base for it to build on. This is the picture of what I'm calling the bottom. Sorry for the quality, lights are on an automatic dimmer.

 

[Diverdown1]

looks like a chalice that was placed upside down