MESOZOIC AND CAINOZOIC DINOFLAGELLATE CYSTS 81 



Range of British Cenomanian forms : diameter of central body 21-47(1 (mean 34.(1), 

 length of processes 4—25(0.. Number of specimens measured, 160. 



Description. The periphragm of the central body at first sight appears to be 

 granular, but at high magnification is seen to be reticulate. The processes, though 

 normally cylindrical or subcorneal, can be mammiform or even saucer-shaped 

 (Text-fig. 17), the latter being 4~5(x in height. Very occasionally closed processes 

 are present being either apical processes or small sulcal processes. 



L. siphoniphorum has been recorded from the Albian of Australia and Roumania, 

 and the Cenomanian of Australia and Britain. 



Remarks. The British Cenomanian specimens from Surrey agree fairly closely 

 with the examples from Australia. The Surrey specimens appear to be smaller, but 

 unfortunately the range of the Australian forms was not given in the description so 

 no true size comparison can be made. 



Fig. 17. Litosphaeridium siphoniphorum (Cookson & Eisenack). A figure illustrating 

 the variation in the size and shape of the processes (based on specimens from the Ceno- 

 manian) . 



