The Burgess Shale is Mecca for paleontologists. Charles Doolittle Walcott, the fourth Secretary of the Smithsonian Institution, discovered this rich fossil bed a century ago, in the summer of 1909, and named it for nearby Mount Burgess. [...] The exquisitely preserved Burgess specimens (most likely entombed by underwater mudslides) include the remnants of soft-bodied organisms, which are rare in the fossil record. The animals inhabitated the ocean floor 505 million year ago, near the end of the Cambrian Period.Reference
 Siobhan Roberts: Evolution's Big Bang • A storied trove of fossils from Canada's Burgess Shale is yielding new clues to an explosion of life on earth. Smithsonian August 2009, Volume 40, Number 5, pp.15-17.