Lithologic and faunal data on the Lower Silurian strata of the eastern United States and Canada were assembled from the literature and compiled on a lithofacies and an isopachous map. These maps show that the sediments thicken and coarsen toward the east, reaching their maximum in southeastern New York and northeastern Pennsylvania. In addition a map is presented to show the distribution of the major faunal elements of the Lower Silurian series. This indicates that the "normal" marine fauna is confined to the carbonate deposits of the central interior, with only Arthrophycus, eurypterids, and a few fish present in the clastic deposits of the Appalachian geosyncline. The biologic affinities and habitat of Arthrophycus are in question, but the Lower Silurian eurypterids and fish probably inhabitated fresh water. The combined lithologic and faunal evidence supports the idea that the major source of the sediments was at the east and/or northeast.