I Propose in this paper to give the evidences for the strati-graphical position of this interesting group, both because the task, so far as I am aware, has not been attempted in detail, and because American geologists themselves are not altogether agreed on the subject, some maintaining the equivalence of the group with our Ludlow, while there are a few who regard it as an easterly extension of the Niagara series of Western New York. Having had an extensive practical acquaintance with the fossils of New York, in the State Museum, and having supplemented cabinet study by work in the field, I venture to hope that I may be able to determine the question to the satisfaction of geologists.