I. Stratigphy. [J. M.] At the end of the year 1859, Mr. Samuel Allport communicated to the Geological Society his discovery of a series of fossiliferous rocks, apparently of Mesozoic age, in the neighbourhood of Bahia (Brazil). In 1870 the same formation was more adequately described by Prof. C. F. Hartt, who regarded it as probably equivalent to the Neocomian of Europe; and, in 1878, the whole of the Cretaceous basin of Bahia formed the subject of a memoir by Dr. Orville A. Derby. The work of all these authors emphasized the importance of systematic collecting from the highly-fossiliferous deposits of the series in question; and it has been my pleasure and privilege, at intervals during the past thirty years, to devote considerable time to this task. Most of the fossil mollusca thus obtained have been monographed by Dr. C. A. White, while the fossil vertebrata have been described by the late Prof. E. D. Cope and Dr. A. Smith Woodward. No summary of results, however, has hitherto appeared; and, as my opportunities tor continuing the work are now almost at an end, I venture to offer to the Geological Society some general observations, to precede a discussion of my collection of vertebrate fossils, which has been prepared by Dr. Smith Woodward As already remarked by Allport, the Cretaceous rocks of Bahia have a general north-westerly dip, but the series is so much disturbed and contorted that the actual dip differs in almost every section. It was, in fact