The genus Semicytherura develops a broad thin calcareous lamella inside the adult carapace, and this feature is one of the characters which define this taxon. However, neither anatomical nor histological studies have so far been done on this character. In earlier works, the lamella was regarded as an extension of the marginal infold, i.e. the “calcified inner lamella cuticle.”
In this study scanning and transmission electron microscope observations have clarified that the lamella is a different structure from the outer lamella cuticle, and that the epidermis does not exist inside the lamella. The lamella is called the “prismatic layer,” because of its calcareous crystal form. Development of this layer causes a restriction of the epidermis, which has a function in respiration and metabolism. Species of this taxon are thought to support their respiratory and metabolic systems by their small body size and low energy of locomotion, or through some specialized structures in the epidermal layers.