Pterotrigonia pocilliformis (Yokoyama)
Mount Futago
Kawarasawa, Ogano city, Chichibu county, Saitama pref., Japan
Early Cretaceous, Mesozoic (130 Ma)
Width: 30 mm. Bivalvia fossil, Trigonia, recovered from sandstone of the Early Cretaceous (130 Ma) Ishido Formation, a member of shallow marine sediments in the Sanchu Graben.