zi8 



MESOZOIC AND CA1NOZOIC DINOFLAGELLATE CYSTS 



Dimensions. Holotype : diameter of central body 75 by 8o\i. Length of 

 processes up to ^jy.. Observed range : diameter of central body 75-95[x. Length 

 of processes up to 37^. Number of specimens measured, 3. 



Description. ?A. patulum has a quadrate archaeopyle resulting from the loss of 

 a single plate. The archaeopyle is surrounded by six processes in the holotype ; 

 these may be precingular but until more specimens are studied definite conclusions 

 cannot be drawn. The processes are considerably broader distally than proximally 

 and have undulose margins. Distal margins of adjacent processes are united. 

 The fibres of the process walls are haphazard in orientation. The walls often appear 

 perforate and this may in part be due to differential staining. The central body is 

 medium brown, the processes tranparent, yellowish green. 



Occurrence. Eocene, London Clay ; Whitecliff, Enborne and Sheppey. 



Remarks. The processes readily distinguish ?A. patulum from other described 

 species. Because of the uncertainty with regard to the type of archaeopyle and its 

 shape, the species is tentatively placed in Adnatosphaeridium. 



OTHER SPECIES 



Other species occurring in the London Clay and here referred to the genus Adnato- 

 sphaeridium are A . fdamentosum (Cookson & Eisenack 1958), A. aemulum (Deflandre 

 1938), A. caidleryi (Deflandre 1938), A. fdiferum (Cookson & Eisenack 1958), all 

 thought to be derived. 



Fig. 58. Adnatosphaeridium patulum sp. nov. Holotype. 

 Archaeopyle (haplotabular) is shaded. 



