Published online by Cambridge University Press: 14 July 2015
Shell structure has been studied in two species of the family Craniidae Menke, 1828, from the Upper Jurassic of East Ukraine and from the Lower Cretaceous of Crimea, South Ukraine. These species belong to the new genus Mesocrania—M. barskovi (Smirnova, 1972) and M. condylata new species. A layer of coarse regular rhomboidal crystallites was discovered between the primary layer of acicular crystallites and the secondary laminar layer. Branching punctae canals were observed in M. barskovi.