FIGURE 12. Extraction of whorl section through ontogeny by successive sections of the triangular mesh with planes perpendicular to the curve-skeleton. 1. Translucent view of the internal volume of the shell with its curve-skeleton. 2. Scheme illustrating two successive cross-sectioning planes perpendicular to and placed along the curve-skeleton. 3, 4. The results of the two cross-sectioning planes, respectively: left figure shows the triangular mesh of the shell and the cutting plane; middle figure shows the triangles of the mesh which intersect the cutting plane; and right figure shows the resulting outline of the whorl section at each examined ontogenetic stage.