地質学雑誌

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Foraminifera listed in p., 357 are found in the Natukawa Limestone at Kutta in the Teradomari Oil-Field, Niigata-ken., Foraminifera from the same place have been described by Prof., H., YABE and Prof., S., HANZAWA (Jap., Jour., Geol., Geogr., Vol., 2)., About a hundred more species are given in our list., Polystomellina dis-corbirordes are not very common in our samples., Pyrgo natukawa n., sp., Holotype: Preserved in the Institute of Geology, Kyoto Imperial University., Description: The first chamber elongate oval, inflated, somewhat compressed., The second also in-flated, rounded, obliquely embracing the previous one., Two chambers visible., In microspheric form, Triloculina young part covered by the last two chambers., Aperture variable, but two principle types A (Fig., 2) and B (Fig., 3) are general: A Aperture crescentiform narrow slit with a flattened semicircular tooth., B., Ape-rture broadly semicircular, or slightly semielliptical, with no tooth., Comparis-ons: Test similar to Biloculina variety of Triloculina cuneata, KARRER, Rep., Voy., Challenger, Zoology, Vol., 9, but distinguished from it by its peculiar apertu-re., Dimention: Diameter, 0., 8mm., Triloculina diameter, 0., 4mm., Observation: This is an interesting Biloculina species containing the relatively large Triloculina young., It is an unusual example of retardation in palingenesis., Type locality: S-akaya, near Kutta, in the Natukawa Limestone of the oil-bearing Tertiary of Eti-go (Niigata-ken), Japan.,

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