38 MESOZOIC AND CAINOZOIC DINOFLAGELLATE CYSTS 



Holotype. B.M.(N.H.) slide ¥.51982(1). 99 feet above base of London Clay ; 

 Sheppey, Kent. 



Dimensions. Holotype : diameter of central body 47 by 49^, length of processes 

 up to 20jx. Range : diameter of central body 41- 5-56^, length of processes up to 

 27(1. 



Remarks. This variety is similar to H. ramosa var. membranacea except that the 

 surface of the central body is granular ; it has only been recorded from the London 

 Clay of England. 



Hystrichosphaera ramosa var. reticulata nov. 



PI. I, figS. 2, 3 



Derivation of name. Latin, reticulatus, net-like — with reference to the reticulate 

 nature of the periphragm. 



Diagnosis. A variety of H. ramosa (Ehrenberg) with central body composed of 

 thin smooth endophragm and reticulate periphragm. Gonal and occasionally 

 sutural processes triangular, taeniate or subcorneal. Gonal processes trifurcate and 

 suturals bifurcate, both types usually terminating distally with small bifurcation. 

 Crests commonly reticulate, proximal except where they extend along processes. 



Holotype. Geol. Surv. Colin., slide PF.3038(i). Lower Chalk, H.M. Geological 

 Survey Borehole, Fetcham Mill, Surrey, at 750 feet depth. Upper Cretaceous 

 (Cenomanian). 



Dimensions. Holotype : diameter of central body 36 by 42^, length of processes 

 up to I4fx. Range : diameter of central body 33-59[i., length of processes up to 17^. 

 Number of specimens measured, 13. 



Remarks. The processes, in the specimens possessing both gonal and sutural 

 processes, are subcorneal. After further study these examples may be separated 

 from the usual type of H. ramosa var. reticulata possessing only gonal processes. 

 This variety is generally similar to H. ramosa var. ramosa but is readily distinguished 

 by the reticulate surface of the central body. 



H. ramosa var. reticulata is present in small numbers throughout the Cenomanian 

 of England. 



Hystrichosphaera cingulata (O. Wetzel) 

 PI. 1, fig- 9 



1933 

 1954 

 1955 

 1963 

 1963 

 1964 



Cymatiosphaera cingulata O. Wetzel : 28, pi. 4, fig. 10. 



Hystrichosphaera cingulata (O. Wetzel) Deflandre : 258. 



Hystrichosphaera cingulata (O. Wetzel) ; Deflandre & Cookson : 267, pi. 6, figs. 4, 5. 

 Hystrichosphaera cingulata (O. Wetzel) ; Gorka : 51, pi. 6, figs. 8-10. 

 Hystrichosphaera cingulata (O. Wetzel) ; Baltes : 587, pi. 4, figs. 12-17. 

 Hystrichosphaera cingulata (O. Wetzel) ; Rossignol : 87, text-fig. G. 



Description. Examples of H. cingulata are common in the Cenomanian of 

 England and are very similar to those described by Deflandre & Cookson (1955) and 



