Cardium refers to a large, extinct species of cockle, these particular fossils are of specimens which lived during the Miocene epoch, a part of the Neogene period, 23 to 5 million years ago. They were found inMadura, Australia and measure 8 cm in size, these particular samples however, are of the internal moulds of the shell. When the animal dies, all of its soft tissues decay or are eaten by predators. This leaves the shell empty and hollow inside, which over times, infills with sediment which over millions of years, lithifies, creating a mould of the inside of the cockles shell. Supplied in a polythene bag with a label, these samples are suitable to explain trace fossils and fossilisation processes.