stratigraphic intervals
   (System) †Cambrian (541.0 - 485.4 Ma)
     1 (Series) †Upper (497 - 485.4 Ma) see Series Furongian Series (497 - 485.4 Ma)
     2 (Series) †Middle (509 - 497 Ma) see Series Series 3 (509 - 497 Ma)
     3 (Series) †Lower (541.0 - 509 Ma)