Final answer:
An ornamental bracket in the form of a scroll with acanthus used under the corona of certain classical cornices is known as a modillion, particularly associated with Corinthian and Composite orders.
Step-by-step explanation:
An ornamental bracket, usually in the form of a scroll with acanthus, used in series beneath the corona of a Corinthian, Composite, or Roman Ionic cornice is known as a modillion. The Corinthian and Composite orders are renowned for their elaborate acanthus leaf motifs, which are prominently featured in their capitals. The volutes or scroll-like elements are characteristic of the Ionic capitals. Unlike these decorative styles, the Doric order is more austere with a simple echinus and abacus and does not employ modillions. The Corinthian order, favored by the Romans, showcases the usage of modillions in various notable architectural monuments, such as the Temple of Mars Ultor, the Pantheon, and the Maison Carrée.