The Silurian Region and Adjacent Counties of England and Wales. Geographically Illustrated By Roderick Impey Murchison F.R.S. F.L.S. Vice President of the Geological Society. Late V.P. of the Royal Geographical Society. Memb. Geol. Society France. Hon. Memb. Royal Irish Acad. and of other Scientific Societies in France, Germany and America. From the Ordnance Survey Coloured in the Field during the Years 1831–8. Drawn and Engraved by J. Gardner, Regent Street, London.
- Author: MURCHISON, Roderick Impey
- Publication place: London
- Publication date: 1839
- Physical description: Large engraved map on three sheets, fine original hand-colour, dissected and mounted on linen, inset geological map of England and Wales.
- Dimensions: 920 by 1470mm (36.25 by 57.75 inches).
- Inventory reference: 1925
The Silurian is a geologic period and system that extends from the end of the Ordovician Period, about 443 million years ago, to the beginning of the Devonian Period, about 416 years ago. As with other geologic periods, the rock beds that define the period’s start and end are well identified, but the exact dates are uncertain by several million years. The base of the Silurian is set at a major extinction event when 60% of marine species were wiped out.