OSTREA. 



371 



180 



Figs. 168-181. — Ostrea vesicu/aris, Lam. Zone of Belemnitella mucronata, Norwich. 168, 169, left and 

 right valves. Norwich Museum, No. 2133. 170, 171, left and right valves. Dr. Eowe's Collection. 

 172, 173, left and right valves. Sedgwick Museum. 174, 175, left and right valves. Norwich 

 Museum. 176-179, left valves. Sedgwick Museum. 178, posterior view of 177. 180, 181, left 

 valve. Dr. Rowe's Collection. 181, anterior view of 180. All x |-. 



