Snappy Tom Cans Seafood Platter

I came home from work and grabbed the lads cat food bowl and noticed that within the remaining dried morsels of breakfast was a match head sized or smaller white spherical ball. It looked like it could be a bone and was very hard. I managed to crush it under a metal weight. Can someone please tell me if they know of a hard tiny white spherical object found within the organs of a sea creature that could be found in a can of seafood platter. Im assuming its open game on every thing from star fish to jelly fish and the odd whales carcass. Any ideas?