According to specialists in the field, there was a body of water that stretched over a large portion of Missouri and surrounding states. At IndianRock.art there is evidence of this previous sea, by way of fossilized marine life.
I posted this stone on a few artifact forums, claiming that there was an octopus trapped in the sediment. I received a mixed response. Regardless of the skeptics, it does appear that someone worked this stone: carving a face into one of the edges. Oddly and par for the course at IndianRock.art, I found a stone of similar composition resting beside it. They are very interesting on a few levels.
Cephalopod Stone – IndianRock.art