The growth lamellae of enamel are first secreted as TOMES' process, and are gradually calcified in relation to the formation of enamel prisms. The pattern of enamel prisms itself is of little use for phylogenetic and taxonomic purpose, as it is essentially circular, so far in the numerous genera examined. On the other hand, the structural pattern of enamel prisms is recommended to be systematically studied for the same purpose, following up KORVENKONTIO and BOYDE.