NB: Look tube shape not opening shape.
Zone A: Intervallum side.
Canal: Pore modified by skeletal structure thikening or by lintels streching. Canal length is greater than perforation diameter.
Lintel: Skeletal structure separating and bounding adjacent pores/canals.
Carcass: Part of wall on intervallum side.
IW: Inner wall.
Type of carcass perforations: inner wall (IW) | |_ Shape of carcass canals tubes zone A (IW)