Plate P6. The modified Kofoid system (as outlined in Fensome et al., 1993b) is used in the labeling of individual plates for the gonyaulacaleans. The Kofoid system is used in the labeling of plates in the peridinialeans. The archeopyle location is denoted by diagonal lines. 1–3. Hystrichokolpoma pusillum Biffi and Manum 1988. Holotype dimensions: central body length (with operculum) = 38 Ám, central body length (excluding operculum) = 30 Ám, central body width = 42 Ám, large processes, length = 8–9 Ám, large processes, breadth = 6–10 Ám, antapical process length = 10 Ám, slender processes, length = 8–9 Ám; (1, 3) dorsal view; (2) ventral view. 4. "Hystrichokolpoma reductum" Zevenboom and Santarelli in Zevenboom 1995 (considered an unpublished manuscript name by the originating authors). Dorsal view. Range of type material: central body length = 40–50 Ám, central body width = 50–72 Ám, process length = 30–40 Ám. 5. Hystrichosphaeridium truswelliae Wrenn and Hart 1988. Ventral view. Range of type material: overall diameter = 72–85 Ám, central body diameter = 39–43 Ám, process length = 8–15 Ám, endophragm thickness < 1 Ám, periphragm thickness < 1 Ám. 6. Hystrichosphaeridium tubiferum (Ehrenberg 1838) Deflandre 1937b, emended Davey and Williams 1966b. Apical view. Holotype dimensions: central body diameter = 33 Ám x 34 Ám. 7. Hystrichosphaeropsis quasicribrata (O. Wetzel 1961) Gocht 1976. Dorsal view. Range of type material: overall size = 100 Ám x 50 Ám. 8. Impagidinium patulum (Wall 1967) Stover and Evitt 1978. Ventral view. Holotype dimensions: diameter = ~55 Ám. 9. Invertocysta tabulata Edwards 1984. Ventral view. Holotype dimensions: length = 90 Ám. 10, 11. Isabelidinium? viborgense Heilmann-Clausen 1985. Holotype dimensions: pericyst length = 58 Ám, pericyst width = 41 Ám, endocyst length = 34 Ám, endocyst width = 33 Ám; (10) ventral view; (11) dorsal view. 12. Kleithriasphaeridium loffrense Davey and Verdier 1976. Dorsal view. Holotype dimensions: central body diameter = 48 Ám x 49 Ám, process length = 31–34 Ám. 13. Kleithriasphaeridium readii (Davey and Williams 1966b) Davey and Verdier 1976. Lateral view. Holotype dimensions: central body diameter = 41 Ám x 45 Ám, process length = 23–29 Ám. 14. Labyrinthodinium truncatum Piasecki 1980. Apical view. Holotype dimensions: diameter = 25 Ám, process length = 5 Ám. 15. Laciniadinium biconiculum McIntyre 1975. Dorsal view. Holotype dimensions: length = 78 Ám, width = 53 Ám. 16. Leptodinium italicum Biffi and Manum 1988. Dorsal view. Holotype dimensions: length (excluding septa) = 60 Ám, width (excluding septa) = 52 Ám, septa = 5–6 Ám. 17, 18. Lentinia serrata Bujak in Bujak et al. 1980. Holotype dimensions: pericyst length = 52 Ám, pericyst width = 32 Ám; (17) ventral view; (18) dorsal view. 19. Litosphaeridium siphonophorum (Cookson and Eisenack 1958) Davey and Williams 1966b. Dorsal view. Holotype dimensions: overall diameter = 76 Ám. 20. Manumiella seelandica (Lange 1969) Bujak and Davies 1983. Dorsal view. Holotype dimensions: pericyst length = 106 Ám, pericyst width = 71 Ám.