The flat or slightly concave side on the stomach lumen side is shown. C–D: Broken gastroliths from Cherax quadricarinatus showing the semispherical and internal aspect of a gastrolith. C: the flat disc visible in the center corresponds to the oldest part of the gastrolith, i.e. the beginning of the calcium storage. D: The homogeneous dense and striated internal structure is well visible on this cross-section.