Plate P19. 1. Hystrichokolpoma bulbosum (Ehrenberg 1838) Morgenroth 1968. Same specimen as Pl. P18, figs. 19, 20. Dorsal surface (800x), courtesy of S.P. Damassa. 2–5. Hystrichokolpoma cinctum Klumpp 1953; (2) optical section (300x); (3) same specimen as 2, ventral surface (300x); (4) same specimen as 2, dorsal survace (300x); (5) dorsal surface (450x), courtesy of S.P. Damassa. 6. "Hystrichokolpoma pseudooceanicum" Zevenboom and Santarelli in Zevenboom 1995 (considered an unpublished manuscript name by the originating authors). 750x. 7. Hystrichokolpoma pusillum Biffi and Manum 1988. Series of successive foci on same specimen (300x), courtesy of S.P. Damassa. 8. "Hystrichokolpoma reductum" Zevenboom and Santarelli in Zevenboom 1995 (considered an unpublished manuscript name by the originating authors). 400x. 9–11. Hystrichosphaeridium truswelliae Wrenn and Hart 1988. Same specimen at different focal depths (400x). 12, 13. Hystrichosphaeridium tubiferum (Ehrenberg 1838) Deflandre 1937b, emended Davey and Williams 1966b; (12) apical surface (350x); (13) same specimen as 12, antapical surface (350x). 14. Hystrichosphaeropsis quasicribrata (O. Wetzel 1961) Gocht 1976. 450x. 15, 16. Impagidinium patulum (Wall 1967) Stover and Evitt 1978; (15) dorsal view of ventral surface (500x); (16) same specimen as 15, dorsal view of dorsal surface (500x). 17, 18. Invertocysta tabulata Edwards 1984; (18) Holotype, courtesy of L.E. Edwards. Both 375x. 19. Isabelidinium? viborgense Heilmann-Clausen 1985. Courtesy of C. Heilmann-Clausen. 700x. 20. Kleithriasphaeridium loffrense Davey and Verdier 1976. 400x.

Plate P19. 1. Hystrichokolpoma bulbosum (Ehrenberg 1838) Morgenroth 1968. Same specimen as Pl. P18, figs. 19, 20. Dorsal surface (800x), courtesy of S.P. Damassa. 2–5. Hystrichokolpoma cinctum Klumpp 1953; (2) optical section (300x); (3) same specimen as 2, ventral surface (300x); (4) same specimen as 2, dorsal survace (300x); (5) dorsal surface (450x), courtesy of S.P. Damassa. 6. "Hystrichokolpoma pseudooceanicum" Zevenboom and Santarelli in Zevenboom 1995 (considered an unpublished manuscript name by the originating authors). 750x. 7. Hystrichokolpoma pusillum Biffi and Manum 1988. Series of successive foci on same specimen (300x), courtesy of S.P. Damassa. 8. "Hystrichokolpoma reductum" Zevenboom and Santarelli in Zevenboom 1995 (considered an unpublished manuscript name by the originating authors). 400x. 9–11. Hystrichosphaeridium truswelliae Wrenn and Hart 1988. Same specimen at different focal depths (400x). 12, 13. Hystrichosphaeridium tubiferum (Ehrenberg 1838) Deflandre 1937b, emended Davey and Williams 1966b; (12) apical surface (350x); (13) same specimen as 12, antapical surface (350x). 14. Hystrichosphaeropsis quasicribrata (O. Wetzel 1961) Gocht 1976. 450x. 15, 16. Impagidinium patulum (Wall 1967) Stover and Evitt 1978; (15) dorsal view of ventral surface (500x); (16) same specimen as 15, dorsal view of dorsal surface (500x). 17, 18. Invertocysta tabulata Edwards 1984; (18) Holotype, courtesy of L.E. Edwards. Both 375x. 19. Isabelidinium? viborgense Heilmann-Clausen 1985. Courtesy of C. Heilmann-Clausen. 700x. 20. Kleithriasphaeridium loffrense Davey and Verdier 1976. 400x.