



i\^ 





.^ ■i: ^- -" 



^J^*^«V*^ 



li 



^ivl.**.*? 



- ■?_ 





Figure 12-1. Parallel annually-formed sub-layers of nacre and 

 simple aragonitic prisms within the inner shell layer of the 

 Atlantic ribbed mussel, Geukensia demissa. 



NOTE: (A) Scanning electron micrograph of vertical fracture surface x240. 

 (B) Acetate peel of polished and etched longitudinal shell section x4(X). 



168 



