What is "elliptocephala"

Elliptocephala is an extinct genus from a well-known class of fossil marine arthropods, the trilobites. It lived from the later part of the Tommotian ( upper Schmidtiellus mickwitzi-zone) to the upper Botomian ( early middle Olenellus-zone). Elliptocephala can easily be confused with Ellipsocephalus, a trilobite genus of the Ptychopariida order.