Ananaspis stokesii
Middle Silurian (Wenlockian)
Much Wenlock Limestone Formation
Wren’s Nest Hill, Dudley, West Midlands
England

9mm trilobite. Extremely rare, especially this fine. Dudley trilobites are highly sought after due to their place in the early history of paleontology. They are nearly impossible to get anymore.

An excellent article on Dudley trilobites can be found here courtesy of the American Museum of Natural History:

Dudley – Crown Jewels Of The Trilobite Kingdom (Opens in new tab)