MESOZOIC AND CAINOZOIC DINOFLAGELLATE CYSTS 



229 



plates 1'" and 5'" bear multibranched linear or annular complexes. There are at 

 least four cingular plates and some sulcal plates having linear complexes. The 

 dorsal surface is convex, the ventral surface depressed. The processes on the ventral 

 surface are closer to those of A . medusettiformis than those of A . coronata, and can be 

 simple or branched distally or proximally. 



A. cf. coronata resembles Systematophora in having process complexes on both 

 ventral and dorsal surfaces. In the shape of the central body, position of the sulcal 

 notch and predominance of soleate complexes however, it more closely approximates 

 to Areoligera with which genus it must be included. 



Dimensions. Observed range : diameter of central body 57-71^, length of proces- 

 ses up to 2J\l. 



Occurrence. Eocene, London Clay ; Sheppey, Kent. 



Areoligera cf. medusettiformis (O. Wetzel) 

 PL 25, fig. 4 



Description. This has similar processes to A . medusettiformis and the same shape 

 of central body. It differs, however, in the presence of process complexes on all the 

 fields and not on the dorsal fields only. The precingular plates bear soleate complex- 

 es, whilst plates 1'" and 5'" have annular complexes. The complexes are unusual in 

 being formed partly from simple processes, especially is this so with those processes 

 nearest to the mid- ventral line. There is a well developed right antapical protuber- 

 ance which is almost in line with the sulcal notch. 



Dimensions. Observed range : diameter of central body, 50-67^, length of 

 processes up to 3fx. Number of specimens measured, 2. 



Occurrence. Eocene, London Clay ; Sheppey, Kent. 



Fig. 63. Areoligera cf. coronata (O. Wetzel). Left, upper (ventral) surface ; right, lower 

 (dorsal) surface, viewed through upper. Archaeopyle shaded. GP, girdle processes ; 

 PS, posterior sulcal processes. 



