TRILOBITES WERE A SWIMMING, BOTTOM FEEDING ANIMAL THAT HAD 3 PARTS: A HEAD (CEPHALON), BODY(THORAX), AND A TAIL(PYGIDIUM) . TRILOBITES WOULD ALSO MOLT THEIR EXOSKELETON . THEY FLOURISHED DURING THE PALEOZOIC ERA,FROM THE CAMBRIAN PERIOD THROUGH THE PERMIAN PERIOD WHEN A MASS EXTINCTION OCCURED--A RANGE OF OVER 500 TO 250 MYA. THE NAME "TRILOBITE" ACTUALLY MEANS "THREE LOBED", REFERRING TO THE AXIAL LOBE WHICH RUNS DOWN THE CENTER OF THE BODY, AND THE LEFT AND RIGHT PLEURAL LOBES, ON EITHER SIDE OF THE AXIAL LOBE. TRILOBITES ARE SAID TO BE THE FIRST OF THE ANIMALS TO EVOLVE TRUE COMPOUND EYES, WHICH WERE MADE OF CALCIUM CARBONATE. THE TRILOBITES I HAVE LISTED ARE JUST A SMALL PART OF THE MANY SPECIES OF THIS VERSATILE ANIMAL. REMEMBER, WHEN LOOKING AT THE PICTURES, THESE TRILOBITES ARE AOUND 400 MILLION YEARS OLD.