During the past autumn, at the kindly suggestion of Prof. Baron von Bichthofen, I spent some months in the study of the strata and fossils of the neighbourhood of St. Cassian. My object was to endeavour, if possible, to determine the most natural subdivisions of these classic strata, and to fix their characteristic fossils. As the results I have obtained are somewhat novel, and may prove of interest to those who are familiar with the enigmatical character of the stratigraphy of the beautiful region of the Dolomites, I may, perhaps, be permitted to give in this place a short summary of my conclusions, in anticipation of a detailed paper upon the subject.