;"Number of epithelial cell layers";Dorsal;Ventral "O. albicans";4;4–5 "O. angrensis";4;4–5 "O. flavoguttata";4;4–5 "O. humilis";4;8 "O. perpusilla";3–4;4–5 "O. trapicheroi";5;5 "O. v-signata";4;4 "S. similis";4;4 "S. hayii";4;4–5 "S. x-signatus";5;7