Much confusion and difference of opinion appears to exist with regard to the classification and nomenclature of the strata which form the lower part of the Cretaceous system, and the chief element of this uncertainty and confusion is the misconception which prevails respecting the proper signification and application of the term Neocomian. The object of the present paper is to explain the continental usage of this name, and by showing its inapplicability to any of our English strata, to prepare the way for a more satisfactory grouping of our Cretaceous rocks.

For many years English geologists were content with the nomenclature employed by the earlier students of the Cretaceous system— Webster, Murchison, Mantell and Fitton. In 1864, however, the French term Neocomian was introduced by Prof. Judd, who adopted it for the Cretaceous portion of the Speeton Clay, and Sir Charles Lyell subsequently used it as a synonym for the whole Lower Cretaceous series in England as distinct from the Upper Cretaceous series or the beds lying above the Lower Greensand.