I. Schemes of Classification In the paper on the Speeton fauna, forming a part of the work which I wrote in conjunction with Mr. G. W. Lamplugh, I attempted to correlate the Upper Jurassic and the Lower Cretaceous horizons of Speeton with their equivalents in Russia and in different parts of Europe, and to give a general scheme of classification of these beds.This scheme may be briefly stated as follows. The Kimeridgian zone of Hoplites pseudomutabilis and Aspidoceras acanthicum is common to different countries of Europe. Above this zone in the Meridional province repose the marine beds of the Tithonic stage, terminating the Jurassic.These beds comprise two substages—the Lower Tithonic, which contains two fossil-zones; and the Upper Tithonic, also containing two zones. To this Tithonic stage corresponds in Southern England the Portland stage sensu lato , including the Lower marine series (Portland, sensu stricto , or Bononian Series), and the Upper freshwater Portland or Purbeck. In Northern France and partly in Southern England three fossil-zones can be distinguished in the marine Portland, namely, the zone of Ammonites portlandicus and Bleicheri , the zone of Virgati , and the zone of A. giganteus . In Yorkshire the equivalents of this series are condensed, and moreover the freshwater Purbeck is replaced by marine beds with Belemnites lateralis , deposited in a separate boreal marine basin. To designate these uppermost horizons of the Jurassic in its marine development, I proposed the name ‘Aquilonian’ stage or substage, including in this term the zone or zones of Ammonites fragilis and nodiger