Plate P23. 1. Renidinium rigidum Prince et al., 1999. Same specimen as Pl. P22, fig. 21. Optical section (500x). 2, 3. Reticulatosphaera actinocoronata (Benedek 1972) Bujak and Matsuoka 1986. Both 850x. 4. Rhombodinium draco Gocht 1955. Dorsal view of ventral surface (300x). 5. Rhombodinium perforatum (Jan du Chêne and Châteauneuf 1975) Lentin and Williams 1977b. Dorsal view of dorsal surface (300x). 6–8. Rhombodinium porosum Bujak 1979; (6) dorsal view, optical section (275x); (7, 8) dorsal view of dorsal surface (275x). 9, 10. Saturnodinium pansum (Stover 1977) Brinkhuis et al. 1992. Apical view; (10) holotype. Both 450x. 11, 12. Saturnodinium perforatum Brinkhuis et al. 1992; (11) scanning electron micrograph (SEM), apical surface. Both 600x. 13–16. Schematophora speciosa Deflandre and Cookson 1955; (13) operculum (950x); (14) dorsal surface (625x); (15) dorsal view of ventral surface (625x); (16) ventral surface (625x). 17, 18. Selenopemphix armageddonensis de Verteuil and Norris 1992; (17) apical view of apical surface (750x); (18) same specimen as 17, apical view of antapical surface (750x), courtesy of L. de Verteuil. 19. Selenopemphix armata Bujak in Bujak et al. 1980. Holotype (575x), courtesy of J.P. Bujak. 20. Selenopemphix dionaeacysta Head et al. 1989b. Courtesy of D. Zevenboom. 750x.

Plate P23. 1. Renidinium rigidum Prince et al., 1999. Same specimen as Pl. P22, fig. 21. Optical section (500x). 2, 3. Reticulatosphaera actinocoronata (Benedek 1972) Bujak and Matsuoka 1986. Both 850x. 4. Rhombodinium draco Gocht 1955. Dorsal view of ventral surface (300x). 5. Rhombodinium perforatum (Jan du Chêne and Châteauneuf 1975) Lentin and Williams 1977b. Dorsal view of dorsal surface (300x). 6–8. Rhombodinium porosum Bujak 1979; (6) dorsal view, optical section (275x); (7, 8) dorsal view of dorsal surface (275x). 9, 10. Saturnodinium pansum (Stover 1977) Brinkhuis et al. 1992. Apical view; (10) holotype. Both 450x. 11, 12. Saturnodinium perforatum Brinkhuis et al. 1992; (11) scanning electron micrograph (SEM), apical surface. Both 600x. 13–16. Schematophora speciosa Deflandre and Cookson 1955; (13) operculum (950x); (14) dorsal surface (625x); (15) dorsal view of ventral surface (625x); (16) ventral surface (625x). 17, 18. Selenopemphix armageddonensis de Verteuil and Norris 1992; (17) apical view of apical surface (750x); (18) same specimen as 17, apical view of antapical surface (750x), courtesy of L. de Verteuil. 19. Selenopemphix armata Bujak in Bujak et al. 1980. Holotype (575x), courtesy of J.P. Bujak. 20. Selenopemphix dionaeacysta Head et al. 1989b. Courtesy of D. Zevenboom. 750x.