Fossil bone of the missing prehistoric animal Jefferson's Earth Sloth (or lazy giant of North America or Megalonyx or Megathere of Jefferson and Mylodon) described by Charles Darwin during his expedition aboard the Beagle. The Zoology of the voyage of H.M.S. Beagle under the command of Captain Fitzroy during the years 1832 to 1836 edited and supervised by Charles Darwin - Fossil Mammalia Part I.??1