Even during the following unstable and cold conditions (intervals
II and III),the microstructural characteristics remained largely
unchanged in shell portions that were deposited onto pre-existing
shell material (shell thickening) with well-ordered first-order
lamellae. In contrast, shell material formed during intervals II
and III that was not deposited onto pre-existing shell material
was characterized by highly unordered microstructures (Fig. 7A
and C)