Plate P21. 1, 2. Membranophoridium perforatum Wilson 1988. Holotype, courtesy of G.J. Wilson; (1) 300x; (2) 400x. 3. "Mendicodinium robustum" Zevenboom and Santarelli in Zevenboom 1995 (considered an unpublished manuscript name by the originating authors). 400x. 4. Nematosphaeropsis downiei Brown 1986. 400x. 5, 6. Octodinium askiniae Wrenn and Hart 1988; (5) 300x; (6) 375x. 7. Odontochitina costata Alberti 1961. Dorsal view (275x). 8. Odontochitina operculata (O. Wetzel 1933a) Deflandre and Cookson 1955. Ventral view (275x). 9. "Odontochitina diversa" Pearce 2000 unpublished thesis name. 300x. 10–12. Odontochitina porifera Cookson 1956; (10, 11) same specimen in ventral view. All 225x. 13. Oligosphaeridium poculum Jain 1977b. 325x. 14, 15. Oligosphaeridium pulcherrimum (Deflandre and Cookson 1955) Davey and Williams 1966b; (14) ventral surface. Both x 325. 16–18. Oligosphaeridium spp. All 325x. 19, 20. Operculodinium divergens (Eisenack 1954b) Stover and Evitt 1978; (20) courtesy of S.P. Damassa. Both 350x.

Plate P21. 1, 2. Membranophoridium perforatum Wilson 1988. Holotype, courtesy of G.J. Wilson; (1) 300x; (2) 400x. 3. "Mendicodinium robustum" Zevenboom and Santarelli in Zevenboom 1995 (considered an unpublished manuscript name by the originating authors). 400x. 4. Nematosphaeropsis downiei Brown 1986. 400x. 5, 6. Octodinium askiniae Wrenn and Hart 1988; (5) 300x; (6) 375x. 7. Odontochitina costata Alberti 1961. Dorsal view (275x). 8. Odontochitina operculata (O. Wetzel 1933a) Deflandre and Cookson 1955. Ventral view (275x). 9. "Odontochitina diversa" Pearce 2000 unpublished thesis name. 300x. 10–12. Odontochitina porifera Cookson 1956; (10, 11) same specimen in ventral view. All 225x. 13. Oligosphaeridium poculum Jain 1977b. 325x. 14, 15. Oligosphaeridium pulcherrimum (Deflandre and Cookson 1955) Davey and Williams 1966b; (14) ventral surface. Both x 325. 16–18. Oligosphaeridium spp. All 325x. 19, 20. Operculodinium divergens (Eisenack 1954b) Stover and Evitt 1978; (20) courtesy of S.P. Damassa. Both 350x.