MESOZOIC AND CAINOZOIC DINOFLAGELLATE CYSTS 89 



They can be simple or bifurcate, distally they are oblate or accuminate. The 

 striae on the periphragm radiate outwards from the bases of the processes over the 

 surface of the central body. 



C. latispinosum has been recorded from the London Clay of Sheppey, Kent and 

 Enborne, Berkshire. 



Remarks. C. latispinosum differs from ? Litosphaeridium truncigerum Deflandre 

 1937 from the Upper Cretaceous of France, in the nature of the broad processes. 

 In ?L. truncigerum these are widely open with denticulate margins, whereas in 

 C. latispinosum they are closed or have a restricted elongate opening with lateral 

 spines developed. 



Cordosphaeridium divergens (Eisenack) 

 PI. 12, fig. 2 



1938. Hystrichosphaeridium sp., Eisenack : 185, text-fig. 3. 



1954. Hystrichosphaeridium divergens Eisenack : 67, pi. 9, figs. 13-16. 



1963. Baltisphaeridium divergens (Eisenack) Downie & Sarjeant : 91. 



19636 Cordosphaeridium divergens (Eisenack) Eisenack : 262, pi. 29, fig. 4. 



Description. Specimens of C. divergens from the London Clay possess an apical 

 haplotabular archaeopyle and the tabulation of the genus Cordosphaeridium. 

 Eisenack (1954) noted and figured the archaeopyle and correctly indicated that the 

 margin of it lay parallel to the equator. Specimens having a reticulate surface, as 

 observed by Eisenack from the Oligocene, are also found in the London Clay. The 

 processes are intratabular, there being at least 4 on each precingular area. In 

 structure they compare favourably with those of the type material. 



Material (Figured). B.M.(N.H.) slide ¥.51750(1). 157 feet above the base of 

 London Clay ; Whitecliff, Isle of Wight. 



Dimensions. ¥.51750(1) : diameter of central body 45 by 47[x, length of proces- 

 ses i4-22fx. Range of London Clay forms : diameter of central body 38-52^, 

 length of processes 12-21 fx. Number of specimens measured, 5. 



Remarks. C. divergens superficially resembles Baltisphaeridium cf. intermedium 

 Deflandre (1938) from the Oxfordian, differing only in its slightly larger size. As yet 

 species belonging to the genus Cordosphaeridium have not been recorded from 

 horizons earlier than the Eocene. 



Cordosphaeridium multispinosum sp. nov. 

 PI. 3, fig. 6 



Derivation of name. Latin, multi, many or numerous ; spinosus, thorny — 

 with reference to the numerous processes. 



Diagnosis. Sub-spherical to ovoidal central body. Thin endophragm and 

 fibrous periphragm giving rise to numerous, more than 45, short fibrous processes. 



