"The terms formation, zone, stage, age, correlation, are clarified. A comparison is made between procedure in stratigraphic classification in the earliest days of William Smith and Oppel and at the present time, and there is found to have been no essential change. A plea is made that stratigraphic nomenclature should be recognized as a separate subject or discipline, with its own rules, which should regularize traditional practice in typography, ban changes of name, and standardize a small number of clearly defined terms."