OSTREA. 



371 



180 



Figs. KiS-lSl. —Osfroa vesicnlaris, Lam. Zone of lichnmitella mi(rcoiia/rt, Noi'wicli. 10S>, Iti'.l, left ami 

 riflht valve.s. Norwich Museum, No. 2133. 170, 171, left and light valves. Dr. Kowe's Collection. 

 172, 173, left and right valves. Sedgwick Museum. 171-, 17.5, left and right valves. Norwich 

 Museum. 17G-179, left valves. Sedgwick Museum. 178, posterior view of 177. ISO, 181, left 

 valve. Dr. Kowe's Collection. 181, anterior view of 180. All x J. 



