"Sections through some species of Globotruncanidae, through Globorotalia tumida and through Gavelinella tumida clearly show that only in the latter species are the chamber septa double and that planktonic foraminifera mostly have simple septa. The reason for these results, contradictory to those of other authors, seems to be the recrystallisation of the thin septal walls in rock-filled specimens. In the present study only air-filled specimens were used. The double septa of the Gavelinellidae are interpreted as a primary wall, covered by the hyaline toothplate; in Globotruncanidae, on the other hand, the toothplate does not cover the primary wall but forms the flap over the umbilical hollow."

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