The Silurian time period lasted from 440 to 410 million
years ago, a time span of 30 million years. The term Silurian was first
used in the 1830s to describe a sequence of rocks in south Wales. The
name Silurian was derived from the name of an ancient British tribe known
as the Silures. These Silurian rocks were defined based on a particular
type of fossil assemblage contained within them. They are located above
the rocks of the Ordovician System and below
the rocks of the Devonian System.