Silurian
/saɪˈljʊərɪən/adjective
1- Geology of, relating to, or denoting the third period of the Palaeozoic era, between the Ordovician and Devonian periods【地质】志留纪的, 志留系的。
1.1
- as noun the Silurian the Silurian period or the system of rocks deposited during it志留纪岩石时期（或系）。
The Silurian lasted from about 439 to 409 million years ago. The first true fish and land plants appeared, and the end of the period is marked by the climax of the Caledonian orogeny.
词源
early 18th cent.: from Latin Silures (denoting a people of ancient SE Wales)+-IAN.