A fossil pearl from the lower Miocene Yamanouchi Member, Akeyo Formation, Mizunami Group at the construction site of Mizunami-Kita Junior High School in Mizunami City, Gifu, Japan
Itoigawa, J., S. Tomida, K. Matsuoka, and Y. Ito. 1981. Fossil pearl from the Pliocene Kakegawa Group, central Japan. Bulletin of the Mizunami Fossil Museum 8: 71-76.