Silurian United States

assemblage of Devonian rocks in Great Britain, Ireland, Norway and northeastern North America, consisting of sedimentary rocks including reddish sandstone

Phacops is a genus of trilobites in the order Phacopida, family Phacopidae, that lived in Europe, northwestern Africa, North and South America and China from the Late Ordovician until the very end of the Devonian, with a broader time range described from the Late Ordovician. It was a rounded animal, with a globose head and large eyes, and probably fed on detritus. Phacops is often found rolled up ("volvation"), a biological defense mechanism that is widespread among smaller trilobites but further perfected in this genus.

Homalonotus is an extinct genus of trilobites in the order Phacopida. It contains several species, including H. armatus and H. roemeri. It is closely related to other trilobites such as Arduennella and Dipleura..