Plate P11. 1, 2. Achilleodinium biformoides (Eisenack 1954b) Eaton 1976; (1) dorsal view of dorsal surface (500x); (2) dorsal view of ventral surface (500x). Courtesy of S.P. Damassa. 3, 4. Achomosphaera alcicornu (Eisenack 1954b) Davey and Williams 1966a; (3) ventral view of dorsal surface (300x); (4) ventral view of ventral surface (300x). 5. Achomosphaera andalousiensis Jan du Chêne 1977. Left lateral view of left lateral surface (500x). 6. Adnatosphaeridium tutulosum (Cookson and Eisenack 1960a) Morgan 1980 (500x). 7. Alisocysta circumtabulata (Drugg 1967) Stover and Evitt 1978. Oblique apical surface (700x). 8. Alisocysta margarita (Harland 1979a) Harland 1979a. Oblique apical surface (700x). 9. Alisocysta reticulata Damassa 1979b. Right lateral surface (550x). 10, 11. Alisogymnium euclaense (Cookson and Eisenack 1970a) Lentin and Vozzhennikova 1990; (10) 850x; (11) 1000x. 12–14. Alterbidinium? distinctum (Wilson 1967a) Lentin and Williams 1985; (12) ventral view of optical section (400x); (13) ventral view of dorsal surface (400x); (14) right lateral view of right lateral surface (400x). 15, 16. Amiculosphaera umbraculum Harland 1979b; (15) oblique lateral surface (400x); (16) optical section (400x). Courtesy of R. Harland. 17. Apectodinium augustum (Harland 1979c) Lentin and Williams 1981. Ventral view of dorsal surface (300x). 18. Apteodinium deflandrei (Clarke and Verdier 1967) Lucas-Clark 1987. Dorsal view of dorsal surface (700x). 19, 20. Arachnodinium antarcticum Wilson and Clowes 1982; (19) ventral surface (300x); (20) optical section (300x).

Plate P11. 1, 2. Achilleodinium biformoides (Eisenack 1954b) Eaton 1976; (1) dorsal view of dorsal surface (500x); (2) dorsal view of ventral surface (500x). Courtesy of S.P. Damassa. 3, 4. Achomosphaera alcicornu (Eisenack 1954b) Davey and Williams 1966a; (3) ventral view of dorsal surface (300x); (4) ventral view of ventral surface (300x). 5. Achomosphaera andalousiensis Jan du Chêne 1977. Left lateral view of left lateral surface (500x). 6. Adnatosphaeridium tutulosum (Cookson and Eisenack 1960a) Morgan 1980 (500x). 7. Alisocysta circumtabulata (Drugg 1967) Stover and Evitt 1978. Oblique apical surface (700x). 8. Alisocysta margarita (Harland 1979a) Harland 1979a. Oblique apical surface (700x). 9. Alisocysta reticulata Damassa 1979b. Right lateral surface (550x). 10, 11. Alisogymnium euclaense (Cookson and Eisenack 1970a) Lentin and Vozzhennikova 1990; (10) 850x; (11) 1000x. 12–14. Alterbidinium? distinctum (Wilson 1967a) Lentin and Williams 1985; (12) ventral view of optical section (400x); (13) ventral view of dorsal surface (400x); (14) right lateral view of right lateral surface (400x). 15, 16. Amiculosphaera umbraculum Harland 1979b; (15) oblique lateral surface (400x); (16) optical section (400x). Courtesy of R. Harland. 17. Apectodinium augustum (Harland 1979c) Lentin and Williams 1981. Ventral view of dorsal surface (300x). 18. Apteodinium deflandrei (Clarke and Verdier 1967) Lucas-Clark 1987. Dorsal view of dorsal surface (700x). 19, 20. Arachnodinium antarcticum Wilson and Clowes 1982; (19) ventral surface (300x); (20) optical section (300x).