Radiolarian Zones Thyrsocyrtis bromia Thyrsocyrtis bromia (1872b, 1875) is adapted provisionally for the purpose of this report until a more detailed investigation can be made in the future.

Contribution No. 691 from the Department of Oceanography, University of Washington. centimeters from the top of the section. Note here that each core is cut into 1.5-meter sections numbered consecutively from the top. For core catcher samples, the abbreviation of CC is used in place of a section number. The position of a figured specimen in the strewn slides is indicated with England Finder coordinates (Ling and Anikouchine, 1967). SYSTEMATIC MICROPALEONTOLOGY Most of the silicoflagellate and ebridian species encountered during the present study have been reviewed in detail recently and their synonymy list has been presented (Ling, 1970, 1971, 1972). In the following, genera and species are arranged in alphabetical order within silicoflagellates and ebridians, and relevant comments or original references describing the named taxa are given wherever deemed appropriate.

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Unusually well preserved Cretaceous radiolarians are observed in the subsurface sections from two drilled sites in the Weddell Sea collected during Leg 113 of the Ocean Drilling Program. Radiolarians from the lithified calcareous chalk of Hole 689B represent the first Campanian-Maestrichtian assemblage which is characterized by abundant Cromyodruppa Iconcentrica, Dictyomitra multicostata, and Protostichocapsa stocki. Abundant Pseudodictyomitra pentacolaensis and Diacanthocapsa sp. 1, on the other hand, are the main constituents of the assemblage from the latest Aptian/earliest Albian diatomite of Hole 693B. These represent the oldest and the highest-latitude reported radiolarian occurrences from the Atlantic sector of the Antarctic Ocean. The assemblages are marked by their low diversity and an absence of low-to mid-latitude zonal indices.