Shell Artifacts or Not

[IndianRiverSonrise]

I found a couple more shells that I think might be artifacts. I don't know about this stuff though. I think on the one cup shaped shell, the bottom has surely been intentionally worn down. What do you think. Here are the photos. Thanks for any ideas.

 

[tmodel]

you lost me. i hope one of the ones who know about salt shells eather are or come on line i wish to hear to so i can learn! Terry