Three important collections of European Devonian and Lower Carboniferous polyplacophorans have been located in United States institutions. The specimens provided a basis for better description of important characters and clarified some taxonomic assignments. Two new polyplacophoran species are in the collections, Helminthochiton carpenteri from the Devonian of Germany and Pterochiton absidatus from the Lower Carboniferous of Belgium. Beloplaxus sagittalis (Sandberger and Sandberger, 1853–1855) is recognized as a multiplacophoran and a new genus and species of turrilepadid, Bouturrilipas scutatus, is proposed.