Quarry stone fossil

[JDKC]

Saw this fishing yesterday. It’s inset in a large boulder laid down as erosion control at the lower end of a dam spillway. I’m very tempted to call it a turtle shell but I have no idea what it is. It’s about 8-9” across and 3-4” deep.

[Kane]

Possibly a sectarian concretion.

[Rockwood]

1 hour ago, Kane said:

Possibly a sectarian concretion.

I think you may have meant septarian concretion. 

I've never seen one presented in quite this way, but it does look like where one had been. 

[Kane]

Yes, I did. Thanks. 

[FossilDAWG]

For some reason, "sectarian concretion" made me laugh.

 

Don

[ClearLake]

Certainly is some type of concretion and not a turtle shell.  The polygons on a turtle shell are much more regular than this piece.  I like the look of this one though, I just want to squeeze it so all the pieces go back together!