The photograph of the whole shell and the SEM images of cross-section of <i>M</i>. <i>galloprovincialis</i> shell.

<p>A: the exterior side of <i>M</i>. <i>galloprovincialis</i> shell; B: the interior side of <i>M</i>. <i>galloprovincialis</i> shell, the white line represents the cutting plane; “AMS”, “AMS-A”, and “AMS-P” represent the area of adductor muscle scar (AMS), anterior side of AMS, and posterior side of AMS, respectively. C: the cross-sectional SEM image of AMS-A, showed nacre (N) on the top layer and fibrous prism (FP) at the bottom of this area; D: enlarged image of nacre from AMS-A; E: the cross-sectional SEM image of central AMS, showed myostracum (M) at the top, nacre (N) at the middle, and fibrous prism (FP) at the bottom of this area; F: the cross-sectional SEM image of AMS-P, showed fibrous prism at this area.