Cambrian Stage 4 is the still unnamed 4th stage of the Cambrian and the upper stage of the 2nd Cambrian series. It follows the 3rd stage and lies below the Cambrian Stage 5. The lower boundary has not been formally defined by the International Commission on Stratigraphy yet. One proposal is the first appearance of two trilobite genera, Olenellus or Redlichia. Another proposal is the first appearance of the trilobite species Arthricocephalus chauveaui. Both proposals will set the lower boundary close to million years ago. The upper boundary corresponds to the beginning of Cambrian Stage 5 which also has not been formally defined yet. Proposals are the first appearances of the trilobite species Oryctocephalus indicus or Ovatoryctocara granulata, dated at approximately million years ago.