knurl

Oakland Museum of California
"I was in the desert in Algeria and I saw a camel (and by the way, it's uggly and it smell bad...) and I decide to ride it. It's not so easy to climb on, but it's funny and it's a tall animal. And after that we saw some Algerians that wanted to buy me trade me for 1500 camels."

I think these are from the Chumash of Southern California. They really prized polished shells. They even gambled. I didn't know that.
Oakland Museum of California

Intuit
Oakland Museum of California