External plates: Plate covering incompletely one or several perforations of a wall.Carcass: Part of wall on intervallum side.IW: Inner wall.
Rims of carcass external plates (IW)
Planar
Arcuate
Waved
S-shaped
V-shaped
Inverted-V shaped
Fused
Denticulate: With indented rims.
Denticulate
Presence of carcass external plates: inner carcass wall (IW) | |_ Rims of carcass external plates (IW)