English: Roughly 60 million years after it lived and died, a 1 cm (1/4 inch) weathered fragment of the shell of a Cretaceous Cremnoceramus deformis eroded from the Fort Hays limestone was deposited in a sand bank of an middle-early Miocene river in northwest Kansas. Over time, this sand was opalized, preserving the remnant fossil. Clearly visible are the prismatic calcitic crystals that grew perpendicular to the surface in the shells of the genus. A much poorer fragment can be seen to the lower right.