During the 1880s and 1890s, the term "Lower Silurian" was in common use in United States geologic literature, whereas use of "Ordovician" was exceedingly rare. The few comments regarding Ordovician which appeared were mostly based on concepts of priority and advocated usage of Lower Silurian. J. D. Dana, author of the most significant textbook of the time, consistently opposed adoption of the term. However, by the early 1900s, Ordovician was widely used in the literature and in 1903 it was adopted for use by the U.S. Geological Survey. There is no record of public discussion of the move away from Lower Silurian. C. D. Walcott, employed by the USGS throughout this interval, may have played a pivotal, but private, role in this change of stratigraphic nomenclature.
Changes in stratigraphic nomenclature by the U.S. Geological Survey, 1968