External plates: Plate covering incompletely one or several perforations of a wall.
Carcass: Part of wall on intervallum side.
Outer wall: External part of the skeleton, composed by a porous carcass, simple or coated by a additional sheath.
Single wall: External part of the skeleton for one-walled cup, composed by a porous carcass, simple or coated by a additional sheath.
Carcass external plates: outer wall or single wall (OW/SW) | |_ Type of carcass external plates (OW/SW) {None} | |_ Shape of carcass external plates (OW/SW) {None} | |_ Direction of carcass external plates (OW/SW) {None}