PLATE XXVII. 

 PISIDITJM SUPINUM, A. Schmidt. 



1 . a-q. 1 Internal aspect of a series of valves of all ages showing 



2. a-x. J variation, from the Pleistocene at Grays, Essex. 



PJSIDITJM PAEVTJLTJM, Clessin. 



3. a-b. Posterior and dorsal view of a pair } f 



. ... . f from Fursoen, 



4. External right view 01 a pair v ._. 



7 . Denmark. 



5. a-b. Internal aspect of a pair 



6. Diagrammatic enlargement of the Hinge. 



PISIDITJM viNCBNTiA^trM, B. B. Woodward, n. sp. 



7. Diagrammatic enlargement of the Hinge. 



8. a-b. Posterior and dorsal aspect of apposed 1 from the 



valves Campinien 



9. a-f. External aspect of a series of valves } (Pleistocene) 



10. a-d. 1 T f , at Soignies. 



. Y Internal aspect of a series of valves 



11. a, b. J ; Belgium. 



*#* The scale in millimetres under each figure, or series of figures, 

 shows the amount of magnification. 



