Hi, @Melissa-VanCleve! I see some bryozoans here. You can use https://macrostrat.org/map/#/z=1.5/x=16/y=23/bedrock/lines/ to figure out the age of these rocks.

Part of what looks like a clam shell.

Thank you

gastropoda shell

Thank you

This looks like some kind of bivalve, but the color almost looks as if it isn’t fossilized. Where did you find it?

Looks like a fossil oyster.

In the creek formed by overflow from a pond next door here in central Missouri

This also looks like fossil oyster, which can be found in Missouri: https://books.google.com/books/about/The_Common_Fossils_of_Missouri.html?id=ij4EsrAruIAC

Thank you!

Looks like a fossilized oyster valve.

Thank you