- Yokoyama, M., 1931a:
- Neogene shells from Karafto and the Hokkaido.
- Journal of the Faculty of Science, Imperial University of Tokyo, Section 2, vol. 3, pt. 4, pp. 185–196, pl. 11.
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- Yokoyama, M., 1931b:
- Tertiary Mollusca from Iwaki.
- Journal of the Faculty of Science, Imperial University of Tokyo, Section 2, vol. 3, pt. 4, pp. 197–204, pls. 12–13.
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- Yokoyama, M., 1932a:
- Tertiary Mollusca from the coalfield of Uryu, Ishikari.
- Journal of the Faculty of Science, Imperial University of Tokyo, Section 2, vol. 3, pt. 6, pp. 221–247, pls. 1–4.
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- Yokoyama, M., 1932b:
- Neogene shells from south Karafto.
- Imperial Geological Survey of Japan, Report, no. 111, pp. 1–15, pls. 1–4.
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