MESOZOIC AND CAINOZOIC DINOFLAGELLATE CYSTS 169 



Material (figured). PI. 2, fig. 6, Geol. Surv. Colin, slide PF.304i(2). Lower 

 Chalk, H.M. Geological Survey Borehole, Fetcham Mill, Surrey, at 650 feet depth. 

 Upper Cretaceous (Cenomanian). Another specimen, PI. 2, fig. 7, at 840 feet depth. 



Dimensions. Figured specimens : diameter of central body 52 by 59fx, length of 

 processes up to ij\l. Range of Cenomanian specimens : diameter of central body 

 5o-68(x, length of processes up to 17^. Number of specimens measured, 5. 



? Cleistosphaeridium flexuosum sp. nov. 

 PL 2, fig. 5 



Derivation of name. Latin, flexuosus, flexuous — with reference to the form of the 

 processes. 



Diagnosis. Central body subspherical to elongate, bearing numerous, broadly 

 acuminate, processes. All processes of approximately same length, slightly fibrous 

 and always flexuous. 



Holotype. Geol. Surv. Colin, slide PF.3045(i). Lower Chalk, H.M. Geological 

 Survey Borehole, Fetcham Mill, Surrey at 840 feet depth. Upper Cretaceous 

 (Cenomanian.) 



Dimensions. Holotype : diameter of central body 29 by 37(x, length of processes 

 up to I7(x. Range : diameter of central body 20 to 45(jl, length of processes up to 

 20(x. Number of specimens measured, 4. 



Description. The most distinctive feature of ?C. flexuosum is the flexuous nature 

 of the broad fibrous processes. The nature of the surface of the central body is 

 difficult to determine and the presence of an archaeopyle has not been recorded. 



This is a rare species throughout the Cenomanian of England. 



Remarks. The nature of the processes easily differentiate ?C. flexuous from all 

 previously described species. This species is tentatively placed in Cleistosphaeridium 

 on the general form of the central body and processes. 



Cleistosphaeridium disjunctum sp. nov. 

 PL 11, fig. 9 



Derivation of name. Latin, dis, asunder ; junctus, joined. 



Diagnosis. A Cleistosphaeridium with granular central body and polygonal 

 archaeopyle. Numerous processes hollow, unbranched, closed distally and proxim- 

 ally, with distal terminations blunt, acuminate, or bearing small spines. Processes 

 regularly arranged. 



Holotype. B.M.(N.H.) slide ¥.51739(2). Eocene (London Clay) ; Whitecliff. 



Dimensions. Holotype : diameter of central body 47-54^, length of processes 

 io-i5fi.. Observed range : diameter of body 30-56jx, process length 10-19^. Num- 

 ber of specimens measured, 13. 



