Portlandia ( Megayoldia ) breviscapha (Yokoyama, 1932)
| 1960. | Portlandia (Megayoldia) breviscapha (Yokoyama, 1932) Syntype Oyama, K. et al. 1960 p. 97, pl. 20, fig. 4 |
| 1959. | Yoldia breviscapha Yokoyama Syntype Makiyama, J. 1959 pl. 86, fig. 5 |
| 1932. | Yoldia breviscapha Yokoyama, 1932 Syntype Yokoyama, M. 1932a p. 245, pl. 4, fig. 5 |
| Condition: | Missing |
| Taxonomy: | Mollusca: Bivalvia: Yoldiidae: |
| Geologic Time: | Cenozoic: Oligocene: |
| Horizon: | Uryu group: Lower Tachibetsu formation: |
| Makiyama, J., 1959: Matajiro Yokoyama's Tertiary fossils from various localities in Japan. Part 3. Palaeontological Society of Japan, Special Papers, no. 5, pp. 1–4, pls. 58–86. (Reference No. 0369) |
| Oyama, K., Mizuno, A. and Sakamoto, T., 1960: Illustrated handbook of Japanese Paleogene molluscs., pp. 1–244, pls. 1–71. Geological Survey of Japan. (Reference No. 0412) |
| 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. (Reference No. 0503) |
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| Ichikawa, T., 1983, no. 9, p. 160. |
| Ichikawa, T., 1983, no. 9, p. 63. |
| Ichikawa, T., 1983, no. 9, p. 389. |
