Late Miocene Mollusca from Tapian Langsat and Gunung Batuta, Sungai Bungalun area, Kalimantan (E. Borneo)

Two rather small mollusc faunas, collected nearly seventy years ago by L. M. R. Rutten, have been examined. Though fairly close together and presumably not much different in age (Preangerian: Tf3), they show no relationship to one another. Tapian Langsat: this locality yielded 11 species all of which occur in Preangerian deposits, particularly in the basal Menkrawit and Gelingseh Beds of the Sangkulirang/Mangkalihat area much farther to the North, there being but a solitary species in common with the classical Javanese Preangerian. Gunung Batuta: consisting of 13 species, this assemblage has, like the corals from the same locality but unlike Tapian Langsat, a number of species (in this case 8) in common with the classical Preangerian, while the relationships with the fauna of the Gelingseh and basal Menkrawit Beds are less noticeable. In both cases the relationships with a number of other Preangerian faunas from East Borneo are weak to non-existent, stressing the individual nature of the various sedimentary basins of East Borneo. Generally similar features in this respect have been emphasized by H. Gerth and J. H. F. Umbgrove concerning the corals, ties with distant assemblages often being much stronger than with nearby faunas.