Shell cast or mold?

[Caroboneferous]

I found this piece outside Kansas City, Kansas.  It was found with some other fossils from the Carboniferous (many shells).   It looks like a cast or a mold?  Maybe a really large Gastropod?

 

Pictures attached. 

[Rockwood]

I don't see any definite indications. There are two things that come to mind though.

I have seen chain corals, Haylesites, exposed laterally this way, or crinoid calyxes can have a similar appearance.

Both could well be mere coincidences however.

[Ludwigia]

I'm not seeing anything other than an interestingly shaped sedimentary rock here.

[Tetradium]

On 7/19/2021 at 4:54 AM, Ludwigia said:

I'm not seeing anything other than an interestingly shaped sedimentary rock here.

Some corals may be easily overlooked. I think this is one of the non hexagonal colonial corals. After all Paleozoic have many weird extinct colonial corals.  

[Ludwigia]

3 hours ago, Tetradium said:

Some corals may be easily overlooked. I think this is one of the non hexagonal colonial corals. After all Paleozoic have many weird extinct colonial corals.  

Can you please show us specifically what you mean with this sample. What are the indications here for you?

[Tetradium]

20 minutes ago, Ludwigia said:

Can you please show us specifically what you mean with this sample. What are the indications here for you?

Never minds. I copied and started to edit one of the picture which I thought was the clearest one. But it turn out to be too irregular. Its the third picture - what I thought was parallel rectangular structures turn out to be very different.