FIGURES 1 - 9 



Fig. 1. Comparison of tabulations of ventral areas of various genera of the Peridini- 

 ales. A, primitive area; B, Ceratocorys horrida; C, Goniodoma polyedricum ; D, Gonyaulax 

 pacifica ; E. Gonyaulax fusiformis ; F. Acanthogonyaulax spinifera ; G. Spiraulax kofoidii ; H, 

 Peridinium crassipes . (For explanation, see pp. 7-8.) 



Fig. 2. Diagram illustrating concepts of relationships of genera treated in this report. 



Fig. 3. A, diagram of cross section of thecal wall of Peridinium in region of suture, 

 simple suture without intercalary zone; B, hypothetical diagram of same following development 

 of intercalary zone. External intercalary zone observed; internal intercalary zone not yet 

 demonstrated. 



Fig. 4. Examples of the three types of first apical plates. A, Orthoperidinium ; B, 

 Metaperidinium ; C. Paraperidinium . 



Fig. 5. Examples of the three types of dorsal epithecal tabulation used by Jorgensen, 

 Paulsen, et al. in subdividing the subgenera of Peridinium . (See text for explanation.) 



Fig. 6. Epithecal tabulation. A, with three intercalary plates; B, with only two inter- 

 calary plates. 



Fig. 7. Diagram showing the dimensions used in the study of body proportions in 

 Peridinium . Ventral view. 



Fig. 8. Diagram showing the dimensions used in the study of body proportions in 

 Peridinium . Apical view. 



Fig. 9. Epithecal plate patterns in the section Oceanica . A, first symmetrical; B, 

 second symmetrical; C, first asymmetrical; D, second asymmetrical; E, intergrade between 

 first symmetrical and first asymmetrical. 



96 



