 you will see these little tiny bone-like structures, these little pegs that are packed together just like the stones in a stone archway. And that's because what you're looking at are the degraded remains of the exoskeletons of ancient single-celled plankton that lived in the ocean around 65 million years ago. And they encased themselves in these intricate, lacy skeletons of limestone. And when they died, they sank to the seafloor.