Notes on the Foraminiferal Genera Laterostomella De Klasz and Rérat and Streptochilus Brönnimann and Resig

Abstract. the biserial foraminiferal genera Laterostomella de Klasz & Rérat (1962) and Streptochilus Brönnimann & Resig (1971) have been described from the Miocene of Gabon and from Miocene to Recent levels of the Pacific and Indian Oceans, respectively. Both genera have since been found in the Upper Cenozoic of other regions: Laterostomella at Rockall Bank in the North Atlantic and in Papua-New-Guinea, and modern Streptochilus specimens were collected with plankton nets in the northern part of the Indian Ocean. The apertural characteristics of Laterostomella and Streptochilus show marked similarities as does the general shape of Laterostomella guembeliniformis with some Streptochilus species. However, other Laterostomella species have a very different form and isotopic data indicate that Laterostomella has a benthic and Streptochilus a planktic life habitat. We conclude that both genera are valid. For the first time SEM pictures of Laterostomella species are presented to show morphological variability, surface texture and aperture types.