Mississippian Rock with Unknown Fossil

This fossils looks like some sort of stem creature. It reminds me of a smoothed blastoid but this could be a pseudo fossil.

It is just a distinct shape but no real lines showing details.

Mississippian Rock

Here is the large rock I have been studying that came from Hodgenville, Kentucky (birthplace of American President Abraham Lincoln).

Here is a calcite or quartz cavity with Fenestella bryozoan around it.

More Mississippian Bryozoans

I am trying to figure out what these rings are on the rock I showed yesterday. This rock has layers of Fenestella all over it.

Is it a base for the bryozoan or maybe part of a blastoid?
All I have found at the Hodgenville, Kentucky site are bryozoan remains and some fragments of brachiopods and gastropods.