Some particles were in point contact where carbonate cements develop, while others were in straight of concavoconvex
Figure 9 shows that when grinding depth was less than 3 [micro]m, although there were some micro concavoconvex
features and clear grinding traces on the machined surface, the overall surface quality was fairly good, so it can be concluded that the manner of material removal was dominated by the ductile mode at this point.
Shell weakly concavoconvex
to almost biplanate, transverse subrectangular with maximum width slightly anterior to the hinge line; anterior commissure rectimarginate.
This configuration is often referred to as either a "saddle joint" or concavoconvex
. Motion at this joint is derived from the differing radii of curvature of the articular surfaces, with that of the metacarpal being 33% larger than that of the trapezium.