44 



MESOZOIC AND CAINOZOIC DINOFLAGELLATE CYSTS 



Dimensions. Figured specimen : diameter of central body 45 by 51(1, length of 

 processes up to iiji, length of apical process 2511. Range : diameter of central 

 body 39-52(1, length of processes 7-1311, length of apical process 20-26(1. Number 

 of specimens measured, 5. 



Hystrichosphaera cornuta var. laevimura nov. 

 PI. 4- %■ 5 



Derivation of name. Latin, laevis, smooth ; murus, wall — with reference to the 

 smooth wall possessed by the central body in this variety. 



Diagnosis. A variety of H . cornuta (Gerlach) with smooth surfaced central body. 

 Gonal and sutural processes short and subconical. A large distinctive apical 

 process present often bearing small lateral spines. 



Holotype. B.M.(N.H.) slide ¥.51752(3). 78 feet above base of London Clay ; 

 Sheppey, Kent. 



Dimensions. Holotype : diameter of central body 43 by 53[i., length of processes 

 up to 12(1. Range : diameter of central body 34-64(1, length of processes up to 14(1, 

 length of apical process 16-32(1. Number of specimens measured, 4. 



Fig. 12. Hystrichosphaera cornuta Gerlach. A specimen from the London Clay. Left, 

 ventral view, plate 3" (the operculum of the archaeopyle) lying within the central body ; 

 right, dorsal view. x c.iooo. 



