The Rotularia is a common element of Jurassic to early Tertiary shallow-water marine faunas but little attention has been paid to its paleoecologic and stratigraphic significance. A large collection of Rotularia from the Lopez de Bertodano Formation with precise stratigraphic control, allows division of the sequence into four local zones. These zones have been used to correlate Seymour Island strata with sediments from Snow Hill Island and tentatively with those from Vega Island and The Naze (James Ross Island), and may be useful in clarifying questions about the general stratigraphy of the James Ross Island Basin. A new subgenus (Austrorotularia) and two species (Rotularia (A.) tenuilaevis and R. (A.) zinsmeisteri) are described.--Modified journal abstract.