I think it may be the very edge of a type of marine snail shell, like right at the opening.. ill see if i can find a pic..
Might not be the Exact species, and it looks to be a fossil, so color is different from original, but i think that scalloped edge opening is what you have a piece of there..
This may be it. A fragment of a brittle star leg, the end that attaches to the main body. This image is a close match. Yours is a fossil, eroded out, and tumbled for awhile.
This may be it. A fragment of a brittle star leg, the end that attaches to the main body. This image is a close match. Yours is a fossil, eroded out, and tumbled for awhile.View attachment 1617901