The Pterygotidae comprise two genera, Pterygotus Agassiz and Erettopterus Salter, and four subgenera. Possible species and subspecies are: 37 for P. (Pterygotus), 7 for P. (Acutiramus), 17 for E. (Erettopterus), 6 for E. (Truncatiramus). The stratigraphic range is Middle Ordovician to Middle Devonian; distribution is worldwide. The morphology of the chelicera is reviewed, showing four joints rather than three. Specimens are described from Estonia, Scotland, Libya, Bolivia, and Northwest Territories; five new species include P. (P.) marylandicus from the Keefer Sandstone, Silurian, Maryland, and E. (E.) saetiger from the Bloomsburg Shale, Silurian, Pennsylvania. A complete checklist, a catalog of synonymy, and a bibliography are included.