MESOZOIC AND CAINOZOIC DINOFLAGELLATE CYSTS 



161 



Diagnosis. Subspherical chorate cysts bearing a moderate number of intra- 

 tabular processes, considered to reflect the tabulation 4', 6", 6c, 6'", ip, 3"". Proces- 

 ses solid, closed distally and branched. Archaeopyle apical. 



Type species. Hystrichosphaeridium cribrotubiferum Sarjeant i960. Upper 

 Jurassic (Cardioceras cordatum Zone) ; England. 



Remarks. The processes usually show a distinct circular arrangement on the 

 surface of central body. The cingular processes are distinctive, being deeply furcate, 

 and with the archaeopyle make orientation easy. 



Surculosphaeridium cribrotubiferum (Sarjeant) 

 PL 9, fig. 6 ; Text-fig. 41 



i960. Hystrichosphaeridium cribrotubiferum Sarjeant : 137, pi. 6, figs. 2, 3, text-fig. 1. 



Emended diagnosis. Subspherical central body bearing moderate number of 

 solid, distally closed, perforate processes. Processes variably branched, sometimes 

 deeply, especially cingular processes. Processes reflect a tabulation of 4', 6", 6c, 6'", 

 IP. 3""- 



Holotype. B.M.(N.H.) slide "^.51735(1). Upper Jurassic (Oxford Clay, Cardio- 

 ceras cordatum Zone) ; England. 



Dimensions. Holotype : overall diameter y$\x, diameter of central body 43 by 

 39[x, length of processes up to 24(x. Range : overall diameters 6o-8opL. Number of 

 specimens measured, 8. 



Fig. 41. Surculosphaeridium cribrotubiferum (Sarjeant) . Holotype. Tabulation as reflec- 

 ted by the processes. Left, oblique ventral view ; right, oblique dorsal view, x 

 c. 600. 



