MESOZOIC AND CAINOZOIC DINOFLAGELLATE CYSTS 



Genus Microdinium Cookson & Eisenack 



Microdinium cf. ornatum Cookson & Eisenack 

 setosum sp. n. . 

 Genus Glyphanodinium Drugg .... 

 Genus Eisenackia Deflandre & Cookson 



C. Genera with epitractal archaeopyle . 

 Genus Rhaetogonyaulax nov. .... 

 Genus Dichadogonyaulax nov. .... 



D. Genera with cingular archaeopyle . 

 Genus Ctenidodinium Deflandre 

 Genus Wanaea Cookson & Eisenack . 



E. Genera with archaeopyles formed by other means 

 Genus Pluriarvalium Sarjeant .... 



Pluriarvalium osmingtonense Sarjeant 

 Conclusions ....... 



VII. Fossil dinoflagellate cysts attributed to BALTISPHAER- 

 IDIUM (R. J. Davey, C. Downie, W. A. S. Sarjeant & G. L. 

 Williams) ....... 



Introduction ...... 



The Species hirsulum (Ehrenberg) and striolatum (Deflandre) 

 Genus Surculosphaeridium nov. . 



Surculosphaeridium cribrotubiferum (Sarjeant) 

 vestitum (Deflandre) . 

 longifurcatum (Firtion) 

 Genqs Exochosphaeridium nov. . 

 Exochosphaeridium phragmites sp. n. 

 Other Species ..... 



Genus Cleistosphaeridium nov. . 



Cleistosphaeridium diversispinosum sp. n. 



ancoriferum (Cookson & Eisenack) 

 heteracanthum (Deflandre & Cookson) 

 flexuosum sp. n. . 

 disjunctum sp. n. 

 Other Species ....... 



Genus Prolixosphaeridium nov. ..... 



Prolixosphaeridium deirense sp. n. . 



granulosum (Deflandre) 

 Other Species ....... 



Other Mesozoic and Cainozoic Species attributed to Balti- 

 sphaeridium ...... 



VIII. The genus HYSTRICHOKOLPOMA (G. L. Williams & C. 

 Downie) ........ 



Introduction ....... 



Genus Hystrichokolpoma Klumpp 

 Hyslrichokolpoma eisenacki sp. n. . 

 var. turgidum nov. 

 unispinum sp. n. . 

 rigaudae Deflandre & Cookson 

 Other Species ...... 



IX. WETZELIELLA from the London clay (G. L. Williams & C. 

 Downie) ....... 



Introduction ...... 



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