232 MESOZOIC AND CAINOZOIC DINOFLAGELLATE CYSTS 



Dimensions. Observed range in London Clay : outer shell, length no-i33[x, 

 breadth 75-103(0. ; capsule, length 55-75(x, breadth 66-86jjl. Number of specimens 

 measured, 13. 



Occurrence. Eocene, London Clay ; Whitecliff, Enborne, Sheppey and Stud- 

 land. Also from the Palaeocene to the Oligocene in Europe and the Lower Tertiary 

 of Australia. 



Deflandrea phosphoritica subsp. australis Cookson & Eisenack 



PL 26, fig. 4 



19616. Deflandrea phosphoritca subsp. australis Cookson & Eisenack, pi. 1, figs. 2, 3. 



Discussion. Only three specimens from the London Clay can be definitely 

 attributed to D. phosphoritica subsp. australis, although intermediate forms to 

 D. phosphoritica subsp. phosphoritica are common. 



Dimensions. Observed range in London Clay : outer shell, length 138-157^, 

 breadth 72-104^, capsule, length 69-75^, breadth ^2-6-Syy.. 



Occurrence. Eocene, London Clay ; Enborne and Sheppey. Also occurs in the 

 Lower Tertiary of Australia (Cookson & Eisenack 1961&). 



Deflandrea denticulata Alberti 



1948. Peridinium cf. galeatum (pars.) Pastiels : 50, pi. 5, figs. 17-20. 

 1959. Deflandrea denticulata Alberti ; 102, text-fig. 1. 



Discussion. The London Clay specimens attributable to D. denticulata are 

 generally smaller than the type material and are sufficiently well preserved to give 

 details of tabulation, determinable from the small acuminate or blunt processes that 

 occasionally delimit the plate boundaries. These indicate the presence of four 

 apical, three anterior intercalary, five postcingular, and as yet unknown numbers of 

 precingular and antapical plates. The archaeopyle is intercalary, resulting from the 

 loss of plate 2a. The tabulation of D. denticulata is thus peridinoid. The small 

 processes, often longer on the prominent apical and antapical horns, are not restricted 

 to the plate boundaries. They have a tendency to be orientated in linear complexes 

 running in an antero-posterior direction. The sutures of the indented sulcus are 

 always denticulate. 



Dimensions. Range in London Clay : outer shell, length 72-126-5^, breadth 

 43-74^ ; capsule, length 37-64^ ; breadth 38-61^, length of apical horn 20-391X. 

 Number of specimens measured, 15. 



Occurrence. Eocene, London Clay ; Whitecliff, Enborne and Sheppey. Also 

 recorded from the Palaeocene to the Lower Eocene in Germany (Alberti 1959ft), and 

 from the Ypresian in Belgium (Pastiels 1948). 



