Priscoan
/prɪˈskəʊən/adjective
1- Geology of, relating to, or denoting the aeon that (in some schemes) constitutes the earliest part of the Precambrian, preceding the Archaean aeon. It extended from the origin of the earth to about 4,000 million years ago, and has left no identifiable rocks.【地质】（太古代前）前寒武纪初期的。
1.1
- as noun the Priscoan the Priscoan aeon前寒武纪初期地质宙。
词源
formed irregularly from Latin priscus 'ancient'+-AN.