Dried and weighed core sediment sample was placed into a beaker with a 3%–5% solution of hydrogen peroxide and sodium diphosphate decahydrate to remove the calcareous fine fraction from radiolarian shells before hydrochloric acid treatment because the calcareous fine fraction sometimes breaks radiolarian shells during intense effervescence in hydrochloric acid solution. After boiling for a few minutes to achieve desegregation of the fine calcareous fraction from radiolarian shells, the sample was sieved and washed through a 63-µm mesh. The desegregated residue was returned to a beaker containing a 3% solution of hydrochloric acid. After dissolution of the calcareous fraction, the residue was sieved through a 63-µm screen and again returned to the beaker. A solution of ~5% hydrogen peroxide with a little sodium diphosphate decahydrate was added to the beaker and then boiled for 20 min or more. Wet residue sieved through a 63-µm mesh was oven-dried at 60°–70°C. The dried material was divided equally using a simple splitter into parts of sample large enough to obtain several thousand specimens per sample. One portion of the divided material was scattered randomly on a glass slide on which thin gum tragacanth was first spread. Material was mounted using Canada balsam and a 24 mm x 40 mm coverslip.
We counted all specimens to the end of the transverse line at which 500 specimens was exceeded. All specimens mounted on a slide were observed to confirm the occurrence of stratigraphic marker species and groups. Species and species groups that are valuable for stratigraphic correlation are recorded in "Appendix A" and illustrated in Plates P1–P17. Radiolarian events recognized in Holes 1218A, 1219A, and 1220A are presented in Table T1. Radiolarian count data for each hole are shown in "Appendix B," "Appendix C," and "Appendix D."