An internally consistent succession of six named regional stages (from youngest to oldest: Sunwaptan, Steptoean, Marjuman, Delamaran, Dyeran, Montezuman), with their boundaries defined by regional extinction events within the trilobite record, is proposed for the trilobite-bearing rocks of Laurentia. Sub-trilobite stage(s) are recommended but unnamed. The three youngest stages have been named previously, but the lower boundary of the Marjuman is shifted downward. The three older stages within the trilobite record are new. If deemed necessary, four regional series are also suggested (from youngest to oldest: Millardan, Lincolnian, Waucoban, and Begadean); each of the three youngest series accommodates two stages.

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