PLATE IX. 



PISIDIUM AMNicuM (Mliller). 



1. a-f. Internal aspect of a series of adult valves, showing 



variation in outline, of the typical form from the 

 Pleistocene at Crayford-Erith > Kent. 



2. a-h. - of the " var. danubialis " from the Pleistocene at 



Grays, Essex. 

 - of young valves of the typical form, from the 



3. a-f} 

 4. a-f. I 



-/. J Pleistocene at Crayford-Erith, Kent. 



\ 1 of the young valves of the " var. danubialis" from 



the Pleistocene at Crayford-Erith, Kent. 



7. a-d. } 



[7 c contains an attached Pearl : the only instance 

 met with.] 



8. a, b. of two adult valves of the intermediate form, from 



the Cromerian at West Runton, Norfolk. 



9. a-f. of a series of valves of the extremely triangular 



form, from the Pleistocene at Grays, Essex. 



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

 shows the amount of magnification. 



