ALBERT

Description: The examination of forty two samples of Sediment coming from the “Golfe de Gascogne” Continental margin (from 150 to 4.200 metres) has established the proof of a fauna rieh in benthic and planktonic foraminifera. This research enables to set up the value of certain foraminiferal associations and to propose a zoned essay based on three major groups touching successively the infralittoral, epibathyal, mesobathyal and abyssal parts.

Description: Young tests studied in very thin sections with the light-microscope with a magnification x 1000 showed, that the results obtained hy Reiss, Be Hemleben and others cannot be true. A primary membrane with sieve-plates where pores are projected by the animal is the first formed membrane; then a hyaline layer is formed beneath the membrane with a general thickness of 2-5 (1 in the Globigerine species. Hie thickness of this primary lamella is also that of the lamella covering the proloculus and the first initial chambers and their septa which always have simple walls. In this primary lamella the pores are spared out and they are at first closed by the sieveplates which, however, may be dissolved soon but for a rim in the wall of the pores. Then a second layer Starts, now at the outside of the primary membrane, beginning with fine knobs between the pores but soon forming a whole layer of clear calcäreous matter. It is in this stage that also the first spines are formed, strengthened at their bases by a mount of calcareous matter; so these spines end at their bases at the primary membrane. The thickening of the outer lamella may continue; this lamella is formed soon after the building of the primary lamella, Not only by means of the study of the last formed chamber of several species of Globigerines this result was obtained, but also by means of the colouring of the layers in Globigerina rubra. It is shown, moreover, that Sphaeroidinella dehiscens cannot be an advanced stage of Globigerina triloba. In Globorotaliid species the primary lamella, as found by Reiss c.s., mostly is slightly thicker than in Globigerines. In this group young specimens were observed with last formed chambers having only the primary lamella covered by the primary membrane also, whereas specimens were found which have septa only built by this lamella. The second, outer lamella is formed soon after the primary lamella, so that many specimens occur which show two lamellae in the wall of the last formed chamber. The result is thus quite similar to that obtained in the Globigerines: the species around Globorotalia are monolamellar too.

Description: Bolli assumed. that at the beginning of an evolutionary trend of planktonic Foraminifera the coiling direction should be at random. Two sequences of such trends were studied, the one of the Globigerina-cretacea-gens (Praeglobotruncana infracretacea- P. gautierensis) in the Albian of Holland, the other of the Globigerina (Globoconusa)- daubjergensis-gens in the Danian of Denmark, to verify this assumption. Both sequences show that in the beginning of an evolutionary trend the percentages of right coiling are distinctly less than 50 % and that later in the evolution the random coiling direction is transgressed towards dominant right coiling. The eventual causes of sudden regressions towards left coiling are discussed.

Description: In their wall-structure specimens from the Miocene (Sphaeroidinellopis seminulina (Schwager) = S. subdehiscens Blow) do not differ from later forms of this gens. The walls consist of an inner calcareous lamella, covered by the primary pseudochitinous lamella, succeeded by a second calcareous lamella in which eventually spines can be detected, and then a third thicker calcareous lamella is added, as in Globigerina rubra (Hofker, 1971, Pl. VI). The difference with Sphaeroidinella is that dorsal secondary apertures are lacking. But young specimens of S. dehiscens from Basal Pleistocene in a JOIDES sample lack these openings also, whereas the chambers following the embryonic ones all show the third thickening lamella. In these pleistocene individuals remmants of the spines are found in the form of fine open canals which do not pierce the chitinous lamella nor the primary calcitic one. Last formed embryonic chambers may show traces of these spines at their outsides. Young specimens of the Recent form, S. excavata Blow, are built as the Miocene ancestor. This recent form shows bullae in many specimens. During this evolution from Miocene to Recent the gens gradually increases its size in the adult specimens, as is found in many other planktonic gentes. Ontogenetically as well as phylogenetically this gens shows no proof of the theory proposed by Be, Hemleben and Bandy, that Sphaeroidinella is the deep water form of Globigerina sacculifera Brady. The forming of secondary apertures in the later larger forms of this gens is also found in many other planktonic genes increasing their size during time, as is the forming of bullae. There is no reason to split off the genus Sphaeroidinellopsis from Sphaeroidinella as the young specimens of the latter genus should in that case be put in Sphaerodinellopsis. In the Recent form the hollows left by the spines are filled up with calcite when the third thickening lamella is formed.