Catherine de Medicis, reine de France after Clouet (Versailles) photo by Gérard Blot
This portrait, after a Clouet original, shows Catherine de Medici wearing a dress with an upswept, crescent, neckline and a partlet covering the space between the neckline of her dress and the neck opening. From the superb Réunion des Musées Nationaux (RMN) site. To find images, go here. When searching for artists - use last names first and do all searching en français si'il vous plait.
RMN has 38 pages of listings related to Catherine de Medici here.