[Proceedings of the symposium 'Molluscan Palaeontology' : 11th International Malacological Congress, Siena (Italy) 30th August - 5th September 1992 / A.W. Janssen and R. Janssen (editors)]: Stratigraphical notes on Macoma (Bivalvia) in the southern part of the North Sea Basin and some remarks on the arrival of Pacific species

The stratigraphical occurrence in the southern North Sea Basin of the marine bivalve genus Macoma is reviewed. New data concerning first and last appearances are presented. Especially the first appearance of Macoma balthica and the last appearances of M. obliqua and M. praetenuis are discussed. M. balthica appears in the late Middle Tiglian (Early Pleistocene). M. obliqua has been found in offshore deposits dating from the climatic optimum of the last interglacial, the Eemian. M. praetenuis occurs in deposits just underlying the Eemian deposits. The age of these underlying deposits is uncertain but may be Late Saalian/Early Eemian. Both latter species were previously considered to be extinct after the late Middle Tiglian. The age of the arrival of 'Pacific' species in the North Sea Basin in the Pliocene is briefly discussed.