The Fulton formation was described from the Fulton Ward, Cincinnati, by August F. Foerste,1 in 1905, and regarded as the basal member of the Eden. The Rogers Gap was named and described in 1914, by Foerste,2 with type section at Rogers Gap Station, Scott County, Kentucky. Neither formation was known in the region of outcrop of the other. Faunally they are much alike, by far the great part of each fauna being common to both. Together they constitute what may be called the Eridorthis nicklesi zone. Uncertainty has existed as to their relationship and areal extent. Bassler 3 has assigned the Rogers Gap to the uppermost Trenton, and, thus, to the pre-Fulton. Others have suggested that the two are possibly correlatives. At the type locality, the Rogers Gap is a part of the Eridotrypa aedilis zone and, thus, typical Trenton. The Fulton in the Cincinnati region is similarly a . . .