What is "cheiruridae"

Cheiruridae is a family of phacopid trilobites of the suborder Cheirurina. Its members, as with other members of the suborder, had distinctive pygidia modified into finger-like spines. They first appeared in the uppermost Cambrian (upper Furongian), and persisted until the end of the Middle Devonian ( Givetian). Currently about 657 species assigned to 99 genera are included.