The study of the sedimentary rocks, stimulated in part by the rise in importance in petroelum geology, is no longer a neglected field. The interest in sedimentology has indeed become wide-spread and the field is at present being attacked by the petrologic-mineralogic approach which employs criteria that can become usable best when put on a quantitative basis. The old stratigraphic-palaeontologic approach, for which criteria used with success in a quantitative way, is culminated by the work of Haug (1) and Grabau (2). Hang first recognized the important distinction between clastics and non-clastic sediments. Grabau followed the suit to divide the sedimentary rocks into three groups: atmogenic hydrogenic and biogenic. These again are subdivided according to composition and texture but the textural subsivisions are treated more important than the compositional ones. The introduction of textural terms such as rudvtes, arenytes and lutytes for the exogenic rocks and spherites, granulite and pulverite for the endogenic rocks has