During a reconnaissance of the Tertiary formations in the western Vogelkop in 1929/1930 for the Bataafsche Petroleum Maatschappij, The Hague, the geologists J.P. Roothaan and J.B. Woolley collected a number of fossil molluscs in the outcrop area of the Klasaman Formation, later to be dated as 'Late Miocene and Plio-Pleistocene' on the basis of foraminiferal studies carried out in the course of a 25 years' search for oil (1935-1960), by the Nederlandsche Nieuw Guinea Petroleum Maatschappij. In 1930, Dr K. Martin made a preliminary examination of the fossils, which in recent years were restudied by the present writer, the number of species identified thereby being raised from 16 to 35. Unfortunately, an attempt to determine the ages of at least the two largest faunules (numbering merely 20 and 16 species respectively, both deriving from the upper part of the Klasaman Formation), more precisely than in Martin's time, failed to give satisfactory results, making it abundantly clear that much more material is needed before one can say more about the ages of these assemblages than that they are 'Miocene/Pliocene', and 'possibly Pliocene'. Palaeontologically however, the fauna is quite interesting. Seven new forms are described, viz., Zoila caputavisensis, Volutoconus hargreavesi aridus, 'Barbatia sorongensis, Arcopsis caputavisensis, Glycymeris caputavisensis, Carditella caputavisensis, and Cardiocardita oostinghi, an eighth, Galeodea papuana, having been described as far back as 1943. Finally, the new Arcopsis altenai, related to A. caputavisensis from Vogelkop, is described from Java on the basis of specimens selected from Martin's syntypes of A. bataviana. Some of the species are of particular interest as they belong to genera whose living species are restricted to Australian waters: these are the new representatives, presumed extinct, of Zoila and Volutoconus, while Amoria canaliculata is still living. There is also a sprinkling of rarely recorded species, Strombus triangulatus and Nemocardium parvulum, and a comparatively large number of small species; also four living species occur not previously recorded fossil.