These fossil sea biscuits were picked up on a limerock road out in the country. Around here limerock is crushed and spread onto dirt roads to stabilize them. Often the gravel will contain these casts of the sea biscuit "test"...(shell). As you probably already guessed, the sea biscuit is an Echinoderm and a cousin of sea urchins, sand dollars, and seastars. These are fossils, but sea biscuits still exist.