I. I ntroductory and D escriptive . Although, during the last twenty years, the Upper Cretaceous strata of England and the Continent have been the objects of detailed investigation, the deposits of the same age, which form so conspicuous a feature in the North-east of Ireland, have been practically neglected. Two observers only, Prof. R. Tate and Dr. C. Barrois, have seriously attempted to classify these formations on definite palæontological principles, but the results at which they respectively arrived differ in several material particulars. The present paper is the outcome of two excursions carried out in the summers of 1895 and 1896: the first connected with, and following on, the Geologists' Association's visit to County Antrim, under the guidance of Mr. A. McHenry; the second aiming at a more detailed examination of the stratigraphy of the same district. The first and second parts will be devoted to the consideration of the various sections visited, together with an account of the results obtained by applying the methods of analysis and microscopical examination previously employed by me in considering the Upper Cretaceous zones of the South of England. In the third and fourth parts it is proposed to examine the theoretical questions arising out of these researches, dealing with the zonal classification of the Irish Cretaceous strata, the probable distribution of the land-masses, and the sequence of physical changes during the period under consideration. My thanks are due to the following members of the Belfast Naturalists' Field Club, who have freely placed their local knowledge