PLATE XLIII. 



Genus — Pleuromya. Agassiz. 



Figs. 



1, 2. r. Orhigniana (Rouillier). Spilsby Sandstone, Donnington. Sedgwick 

 Museum, Cambridge. I a, right valve ; 1 //, dorsal view. 2, orna- 

 mentation X 12; II, near middle of valve ; /', near the ventral 

 margin ; c, between n and A. (P. 25().) 



G enus — Lion sth a, Med-. 



3, 4. L. {Psilomi/a) gigantea (Sow.). Upper Greensand, Blackdown. Sedgwick 

 Museum. 3 a, left valve ; b, hinge of the same. 4, umbo of right 

 valve X <>. (P. 2.J7.) 



5. L., sp. Red Limestone, Hunstanton. British Museinn, No. 83628. 

 (I, right valve; h, dorsal view; c, ornamentation x 0. (P. 258.) 



Gen us — Crsri ha i; i a, N(( rdo. 



G. C. SalxniiUana (Pict. and Cainp.). Uault, Folkestone. Museum of 

 Practical Geology, No. 23821. n, left valve X Ig; b, dorsal view 

 X n. (P. 259.) 



