[From introduction:]
Professor Doctor Klaus J. Müller, Technishe Universitat Berlin, West Berlin, Germany, has kindly given me for description a suite of scolecodonts, fossil polychaete annelid jaws, collected and prepared by him in 1956. The specimens came from 25 feet below the top of the formation at the Sheffield type locality in the pit of the Sheffield Brick and Tile Company, just south of the town of Sheffield, Section 8, T934N, R20W, Franklin County, Iowa. The Sheffield shale is correlated with the Upper Devonian (Canadaway) of New York. Besides the scolecodonts this bed contains conodonts and casts of poorly preserved brachiopods. On the basis of the conodonts the age of the Sheffield shale may be Lower Famennian. The scolecodont fauna does not correspond to any other described material although some comparisons might be made with the Alfred, New York, forms if they were better illustrated and described.