1937 Volume 1937 Issue 7 Pages 42-49
A study of various collections of foraminifera now stored in the collection of the Institute of Geology and Palaeontology, Tôhoku Imperial University, Sendai, Japan, has rendered possible the review of the Japanese species of Cassidulina, both fossil and recent.
There are 12 species belonging to the genus Cassidulina in Japan; among them 4 species, namely, C. japonica n. sp., C. yabei n. sp., C. setanaensis n. sp., and C. sublimbata n. sp. are distributed only in northern Japan, both as recent and fossil, and are not known from the Pacific side of Japan. On the contrary, the other 8 species, namely, C. subglobosa BRADY, C. subglobosa parva n. subsp., C. subglobosa depressa n. subsp., C. sagamiensis n. sp., C. kadusaensis n. sp., C. orientale CUSHMAN, C. pacifica CUSHMAN and C. laevigata D'ORBIGNY (?), occur only in the recent or fossil materials from the Pacific side and not in those from the Japan Sea side.
The distribution of these interesting forms are the subject of this article and descriptions of the new species or subspecies will appear in another article.
The writers here propose the following two different provinces of the marine Neogene from the view point of distribution of Cassidulina.
1) Cassidulina province of the Japan Sea type:-This includes the Neogene formations in the prefectures of Aomori, Akita Niigata, Toyama, Isikawa and HokkaidÔ.
2) Cassidulina province of the Pacific type:
This includes the Neogene formations of Bôsô and Miura Peninsulas, the Kakegawa District and Aki-gun in KOti prefecture.
The former province seems to be closely related to the Neogene Oil-field of Japan and it is noteworthy that the allied species are commonly found in the Plio-Pleistocene of California.