Presents a study that examined the close taxonomic affinity of three suborders of the Corynexochida that come from silicified protaspides of a Lower Ordovocian Leiostegium species. Description of protaspides; Comparison of protaspides of Ptarmigania Aurita and Leiostegium ap. aff. L. formosum; Taxonomic implications of protaspid morphologies.