Plate XVII. 



Figs. 1 I 3. Ostrea plicata, Chem. la. Upper valve, outside, lb. The same. 



inside. 2a. Lower valve, outside. 2b. The same, inside. 3. Lower 



valve, inside. Otsu. p. 163. 

 Fig. 4. Area kobeltiana. Pils. Left valve, a. Outside, b. Inside, c. Seen from 



the beak-side. Shimo-Miyata. p. 163. 

 Fig. 5. Area decussata Sow. Left valve. Enlarged, a. Outside, b. Inside. Ko- 



shiba. p. 165. 

 Fig. 6. Parallelodon oblicmatus Yok. Left valve. Enlarged, a. Outside, b. In- 

 side. Yokosuka. p. 170. 

 Figs. 7, 8. Area symmetrica Eve. Enlarged. 7. Left valve. 7a. Outside. 7b. 



Inside. 7c. Seen from above. 8. Eight valve. 8a. Outside. 8b. 



Inside. Naganuma. p. 166. 

 Fig. 9. Area inflata Eve. Left valve. Outside. Naganuma. p. 167. 

 Figs. 10, 11. Pectunculus rotundus Dkr. 10. Left valve. Yonng form. Enlarged. 



a. Outside, b. Inside. 11. Left valve. Grown form. a. Outside. 



b. Inside. Naganuma. p. 167. 



