Cambrian Series 2 is the unnamed 2nd series of the Cambrian. It lies above the Terreneuvian series and below the Cambrian Series 3. Series 2 has not been formally defined by the International Commission on Stratigraphy, lacking a precise lower and upper boundary and subdivision into stages. The proposed lower boundary is the first appearance of trilobites which is estimated to be around million years ago. The upper boundary is proposed as the first appearance of either the trilobite species Oryctocephalus indicus or Ovatoryctocara granulata, currently estimated to be around million years ago.