Continuing the mega trilobite binge posts - This is Deiphon barrandei, a type of Silurian lens-faced, or phacopid, trilobite. They typically have an enlarged glabella, the space at the top of the cephalon, equivalent to the space above our eyebrows. This is often filled with fats or oils, and is thought to have been either designed to keep them buoyant, or designed to store digestive systems and thus being a signal of a predatory type of trilobite. Their pleural lobes (on the thoractic segment) are interesting in that they fan out to replicate fish skeletons.
This sample was found in Malvern, Worcestershire, UK.