A method is outlined for cataloguing sedimentary rocks according to type, structure, texture, and associations, based largely on F. J. Pettijohn's (1957) treatment of sedimentary rocks. For example, conglomerates and breccias are designated P1, sandstones P2. Orthoquartzites carry a P21 designator. A first-cycle orthoquartzite would be catalogued P211At, the 'A' representing the first sample to be catalogued, and the 't' prepared thin section. Samples of this type from other formations would be designated by 'B', etc.; samples from the same formation but different localities would be P211A2, etc., and a series of samples from the same locality would be P211A2a, P211A2b, etc.