A stage (464–460.9 Ma ago) of the Ordovician in the Middle Champlainian series of N. America, preceded by the Llanvirn and followed by the Ordovician V.
科学参考收录了60776条科技类词条，基本涵盖了常见科技类参考文献及英语词汇的翻译，是科学学习和研究的有利工具。