A bivalve cast encrusted in basal rock. The empty spaces were occupied by the now gone, dissolved shell.
https://sites.northwestern.edu/monroyrios/files/2015/08/cropped-DSC02354-26iwtth.jpg
cropped-DSC02354-26iwtth.jpg
A bivalve cast encrusted in basal rock. The empty spaces were occupied by the now gone, dissolved shell.
https://sites.northwestern.edu/monroyrios/files/2015/08/cropped-DSC02354-26iwtth.jpg