The boundary between Upper and Lower Bathonian has recently been exposed in a clay pit in Hildesheim (near Hannover, Northern Germany). The section is dated by the ostracode and ammonite fauna; the guide ostracode Glyptocythere obtusa is described. — A layer of corroded pebbles (with Lithodomus-hoXes) indicates a hiatus at the boundary. A Statistical analysis of common foraminiferal species is based on 40 samples (5 cm.-spacing); some ecological conclusions are discussed.