MESOZOIC AND CAINOZOIC DINOFLAGELLATE CYSTS 101 



Homotryblium tenuispinosum sp. nov. 

 PI. 4, fig. ii ; PL 12, figs, i, 5, 7 ; Text-fig. 21 



Derivation of name. Latin, tenuis, thin ; spinosus, thorny — with reference to the 

 rather slender processes. 



Diagnosis. Spherical central body with wall composed of thin layers — smooth 

 inner endophragm, outer strongly granular periphragm. Processes erect or curved, 

 tubiform, simple, open distally with serrate or aculeate margin, rarely perforate 

 Width of processes variable. 



Holotype. B.M.(N.LL) slide ¥.51756(1). Metropolitan Water Board Borehole 

 No. 11 at 53 feet depth, London Clay ; Enborne, Berkshire. 



Dimensions. Holotype : diameter of central body 41 by 48^, length of processes 

 20-25(x. Range : diameter of central body 41-57^, length of processes i3-32fx. 

 Number of specimens measured, 8. 



Fig. 21. Homotryblium tenuispinosum sp. nov. A specimen from the London Clay, 



antapical view, x c. 950. 



