 The fossils of the Burgess Shale , like the Burgess Shale itself , formed around 505 million years ago in the Mid Cambrian period . They were discovered in Canada in 1886 , and Charles Doolittle Walcott collected over 60 @,@ 000 specimens in a series of field trips up from 1909 to 1924 . After a period of neglect from the 1930s to the early 1960s , new excavations and re @-@ examinations of Walcott 's collection continue to discover new species , and statistical analysis suggests discoveries will continue for the foreseeable future . Stephen Jay Gould 's book Wonderful Life describes the history of discovery up to the early 1980s , although his analysis of the implications for evolution is largely superseded . 
