Annulus (plur. annuli): Ring-shaped (annular) plate separating horizontal rows of pores.
Tabula (plur. tabulae): Transverse porous partition linking both walls of a two-walled cup.
Carcass: Part of wall on intervallum side.
IW: Inner wall.
Type of carcass external plates (IW) | |_ Relationship between carcass annuli and tabulae (IW)