xii. BIVALVE SHELLS. 303 



Pinna lanceolata. Sow. C. 0. 



mitis. Phil. C. G. Studley. 

 Placunopsis similis. Whit. C. O. Bullingdon. 

 Trichites Plotii. Lhwyd. C. O. Heddington. 



In this list of monomyaria the usual oolitic groups appear 

 gathered round avicula, lima, ostrea, and pecten; gryphsea being 

 abundant in the Oxford clay and lying in several extensive floors, 

 but scattered and comparatively rare in the strata above. A small 

 smooth oyster is so abundant in the shelly oolitic layers as almost 

 to constitute beds, but the valves are seldom associated, while, 

 on the other hand, Ostrea gregarea forms in these same beds 

 large coherent masses with united valves. 



DlMYABIA. 



Arcasemula. Phil. C.O. Heddington. 



subtetragona. Mor. 0. C. 

 Astarte extensa. Phil. C. 0. Heddington. 



ovata. Smith. C. 0. Heddington, Bullingdon. 



rhomboidalis. Phil. C. 0. Marcham. 

 Cardium Crawfordii. Whit. C. 0. 

 Corbis laevis. Sow. C. 0. Heddington. 

 Corbula MacNeillii. Mor. O.C. 

 Cucullsea concinna. Phil. O. C. 

 contracta. Phil. C.O. 

 Cypricardia isocardina. Buv. C. 0. 

 Cyprina dolabra. Phil. C. O. 

 Goniomya literata. Sow. C.O., C.G. Studley. 

 Isocardia tumida. Phil. C. G. 

 Leda Phillipsii. Mor. O.C. 



Lithodomus inclusus. Phil. C. 0. Heddington, Cumnor. 

 Lucina crassa. Sow. C. O. 



lirata. Phil. O.C. 



polita. Phil. C.O. Bullingdon. 

 Modiola bipartita. Sow. C. G. Studley. 



cuneata. Sow. C.G. Studley. 



pulchra (?). Phil. C. O. 

 Myacites calceiformis. Phil. 



recurvus. Phil. O.C. St. Clement's. C.G. Studley. 

 Nucula elliptica. Phil. 0. C. St. Clement's, Oxford. 



nuda. Phil. 0. C. St. Clement's, Oxford. 

 Opis corallina. Lye. C. 0. Bullingdon. 



Phillipsii. Mor. C.O. 

 Pholadomya obsoleta. Phil. C. G. Studley. 

 Quenstedtia laevigata. Phil. C. 0. 

 Sowerbya Deshaysii. Buv. C. 0. Bullingdon. 



triangularis. Phil. C.O. Heddington. 

 Tancredia curtansata. Phil. C. O. 



