The ultrastructure of pristine shells of Jurassic and Cretaceous lytoceratid and perisphinctid ammonoids indicates that flares and parabolae represent homologous structures. Both mark an interruption of shell growth. We dismiss earlier interpretations of parabolae as actual aperture. relics of resorbed apophyses or superstructure of the musculature associated to a semi-internal shell. https://www.roneverhart.com/5-11-FLEX-SHOTGUN-AMMO-POUCH/