Brachiopods are in the form of the two hinged shell type. A group was abundant in the Palaeozoic and are important for stratigraphic purposes.
They are also important indicators of climate and sea depth in ancient times. As a sea inundated an area of land the successive layers of sediment contain fossils of brachipods that lived in water of progressively increasing depth.
Pentamerus oblongus is a rather special brachiopod as it is so numerous in areas of Salop and adjoining counties to form beds of rock where it is the dominant fossil (the Pentamerus Beds).
The name is derived from the five fold symmetry often seen in its fossil form. When seen in section the fossil often resembles arrow heads, and this led to the name Government Rock after the government issue clothing for convicted prisoners which used to be covered in small arrow heads.
Pentamerus oblongus lived in the middle Silurian and can be found in the county of Salop, U.K..