May be blazoned a “viper,” a “snake,” or any period variety of snake. This arrangement with a serpent azure or vert is restricted as a badge of the Visconti family of Milan, where it is known as the “biscione.”
Two Tudor Books of Arms (Page 37). Based on a mid-16th C. copy of a late-15th C. manuscript. https://archive.org/details/twotudorbooksofa00fostuoft/page/n9/mode/2up
Joseph Foster