NUMBER 40 . 25 



FIGURE 19. Images from Hiatella-etched cavities in C. couipactiim from southern Labrador. (A) Ten years of growth with ridges and 

 valleys for each year (summer, top arrow; winter, bottom arrow). (B, C) Surface of summer-fall ridge showing dense interhlament crystals 

 (vertical arrow) maintaining structural integrity (horizontal arrow in C shows inner radial crystals). (D) Winter valley showing the break- 

 ing out of minimal interhlament crystals (horizontal arrows) and the integrity of individual cells and their organic radial-crystal-embedded 

 walls (vertical arrow). (E) Oblique view of the ridge side, showing the intermediate breakdown stage and the great difference between fine 

 inner-wall crystals (vertical arrows) and large, angular interfilament crystals (horizontal arrows). 



