Here are four extinct Florida Sea Cow [Manatee/Dugong] rib pieces in various sizes but with a bit different coloration due to the certain kinds of minerals found in the sediments that they were buried in...A white/tan color [fresh from the phosphate clays], another is black, while another is a  brown, and finally an unusual bluish hue...

[What you see is what you get, we have six examples of this ...Only $10 plus $5 shipping!