National Geographic : 1956 Mar
© National Geographic Society + Ages Have Not Dimmed the Luster of Coiled Ammonites Dipped in water, these extinct relatives of the pearly nautilus seem to take fire. Navajo medicine men value them as charms. Paleontologists find them a key to earth's time secrets. Some ancient shells exceed six feet in diameter, a record for coiled mollusks. Olan rloLograIpner vvllaru on. 'JuIver + Jawbone Tinged with Green Belonged to an Ice Age Rabbit in Arizona Copper solutions stained the bone (three times nat ural size). Lower left: Neritina, a fossil snail from the Caribbean, retains its original black and white. Right: Cranaena,commonly called lamp shell, has pre served its maroon bands about 290 million years.