Identity please

[IndianRiverSonrise]

This bone is about one inch in length. When viewed from an end it has a triangular shape. The base of the triangle has a slightly concave surface and is smooth. The other two surfaces, as I think you can see, have ridges running the length of the bone. It appears to me to have been cut but I don't know. When measured around, the three sides of the triangle are about 1.25 inches each. Here are the photos. Oh, they were found on a beach in central Florida. One picture is shiney because it was still wet from washing.
Thanks for any info.