Good evening, I recently picked this up on one of my hikes I took a couple days ago in Benton County, Missouri. It was in thick woods and pretty shady, so I really wasn't able to make out anything but crinoid bits. I almost chucked it away, but thought I would keep it anyway and I'm glad I did. No apparent formation around but it appears to be Burlington/Keokuk crinoidal limestone. I'm not much of a gastropod fellow, but this appears to be one to me (possibly Straparolus?). I haven't done much prep, just enough to see the lines I saw after scrubbing it with a toothbrush and warm soapy water. Not sure if it could be id'd at this stage or even when I fully prep it (maybe too weathered?), but i figured it would be worth asking others, thanks in advance.
Jackson G