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FlQS. 143-153.— Osirea vesicularis. Lam. HS-l-to. Upper Grc'ens;md (zone of P. asper), Warminster. 

 Museum of Practical Geology, Nos. 259-18, 25<).50. US, left valve. l-H, right valve. 145. anterior 

 view of 144 showing hoth valves. 14(i. Zone of ilicraster coi-niif/iiiHioii, 'Witheringtou, Dr. 

 Blackmore's Collection. Interior of left valve. 147. Zone of Aciinocamax quudratus. East 

 Hamham. Same Collection, liight valve. The left valve is entirely attached to the convex 

 surface of an echinoid. 148, 14!). Zone of ^^craster cor-anfiuiniini, Graveisend. Hritish Museum, 

 No. L. 20991. Exterior and interior of a left valve. l."jtAl53. Zone of BeUmnilclla murronata, 

 Norwich. 150, right valve, Britisli Museum, No. L. 20616. 151, Dorsal view of l.JO showing both 

 valves ; the left valve entirely attached to a nearly flat surface. 152, 153. Sedgwick Museum. 

 Left and right valves. 146, 14", natural size. Otlier figures x J. 



