Boudin (torus)

A ring at the bottom of a colonne (column), more or less the same as an astragale (astragal).
Boudin means literally black pudding.
These columns are to be found in the déambulatoire (ambulatery) of the Notre-Dame-de-la-Nativité in Bois-Sainte-Marie.
See also tore (synonym).

Notre-Dame-de-la-Nativité - Bois-Sainte-Marie