Cretaceous life?

[Brandy Cole]

Most of what I find in southeast Texas is mio-pleistocene, and fresh water based.  But at times older cretaceous stuff washes down.

 

Since it's rare here, I'm completely clueless as to differences between oysters, corals, rudists and things but would like to learn more.

 

I found this a while back and it seems to have very distinct patterns on the outside and inside. From searches, I thought maybe a broken piece of rudist, but I wouldn't know one if it bit me.  It just doesn't look like normal rock to me.

 

Any guidance would be appreciated.

 

@JohnJ

[Tidgy's Dad]

Very interesting.

A sponge, perhaps? 

[Lone Hunter]

I was just fixing to say same thing!

[Brandy Cole]

Something like Porifera maybe?