164 



MESOZOIC AND CAINOZOIC DINOFLAGELLATE CYSTS 



The presence of an apical archaeopyle and the distinctive deeply furcate cingular 

 processes make orientation of this species relatively easy. A number of well preserved 

 specimens were studied and from the positions of the intratabular processes the 

 reflected tabulation appeared to be 4', 6", 6c, 6'", ip, 3'". The test of the original 

 dinoflagellate is tentatively reconstructed in the accompanying figure (Text-fig. 41). 



The reflected tabulation of S. longifnrcatum is the same as in 5. cribrotubiferum 

 (Sarjeant, i960) ; however, the latter possesses characteristically perforate processes. 



Material (Figured). PI. 8, fig. 11, Geol. Surv. Colin. PF.3042(i). Lower Chalk, 

 H.M. Geological Survey Borehole, Fetcham Mill, Surrey at 840 feet depth. Upper 

 Cretaceous (Cenomanian). Another specimen, PI. 8, fig. 7, FM. 730/2, at 730 feet 

 depth. 



Dimensions. Figured specimens : diameter of central body 32 by 37^, length 

 processes 20-24^. Range, lateral view : diameter of central body 30-47^ ; apical 

 view : diameter of central body 36-50^ ; length of processes i4-2()[x. Mean 

 diameter of archaeopyle, 20[jl. Number of specimens measured, 24. 



/' / 3 " 



4" \ «* 



_£i-L__?i__ 



4c 1 



\ 2"'\ 3'" 



4'" / 5* 



Fig. 44. Surculosphaeridium longifurcatum (Firtion). 

 tabulation of the dinoflagellate. 



The probable original 



