Lapworth, recognizing that the fossil fauna in the disputed strata were different from those of either the Cambrian or the Silurian periods, realized that they should be placed in a period of their own.Itokasi.. 
jẹ́ ará orílẹ̀-èdè Nàìjíríààìtọ́kasí àwọn Ọjọ́ìbí níàwọn ara Nàìjíríà..