MESOZOIC AND CAINOZOIC DINOFLAGELLATE CYSTS 83 



? Litosphaeridium crassipes (Reade 1839). Upper Cretaceous ; England. 

 ? Litosphaeridium flosculus (Deflandre 1937). Upper Cretaceous ; France. 

 ? Litosphaeridium truncigerum (Deflandre 1937). Upper Cretaceous ; France. 



Genus CORDOSPHAERIDIUM Eisenack 1963& : 261 



Emended diagnosis. Sub-spherical chorate cysts, with central bodies composed 

 of two distinct layers, periphragm variably developed, forming well developed 

 processes, tubiform to buccinate, solid or hollow, intratabular and reflecting a 

 tabulation of 1', 6", 6c, 6"', (ip), 1"" and a variable number of sulcal processes. 

 Apical archaeopyle haplotabular never possessing zig-zag margin. 



Type species. Hystrichosphaeridium inodes Klumpp 1953. Eocene ; Germany. 



Remarks. The genus Cordosphaeridium differs from related genera in the form 

 of the archaeopyle. The archaeopyle has the shape of a convex triangle with 

 rounded corners. At first sight it appears to be precingular but by study of the 

 process arrangement it has been shown to be apical in position. It is formed by the 

 loss of the single apical plate, the resulting archaeopyle being termed haplotabular 

 (latin, haplo, single). The processes are usually strongly fibrous and can be either 

 open or closed distally. There is little differentiation in the size of the processes, the 

 cingulum processes being often, but not constantly, larger. The number of processes 

 per plate within this genus varies considerably and it is probable that at a later date 

 it will be necessary to sub-divide this genus taking this fact into account. 



This genus was proposed by Eisenack (19636) for forms possessing characteristically 

 fibrous processes. Since it has been shown that hystrichospheres are cysts of 

 dinoflagellates, the systematics of this group should be based on the tabulation 

 reflected by the arrangement of the processes. It is therefore considered that the 

 reflected tabulation is a better diagnostic feature than the fibrosity of the processes 

 and the diagnosis has been emended accordingly. Other reasons against using the 

 fibrosity of the processes as a generic distinction are that it is very variable within 

 this genus and also that fibrous processes have been observed in other genera which 

 have a distinct and different tabulation. 



Cordosphaeridium inodes (Klumpp) 

 PL 3, fig. 9 ; Text-fig. 18 



1953 

 1953 

 1955 

 1961 



1963 

 1963 



Hystrichosphaeridium truncigerum Cookson : 114, pi. 2, figs. 21-23. 

 Hystrichosphaeridium inodes Klumpp : 391, pi. 18, figs. 1, 2. 

 Hystrichosphaeridium inodes Klumpp ; Deflandre & Cookson : 277, pi. 8, fig. 7. 

 Hystrichosphaeridium inodes Klumpp ; Gerlach : 186, pi. 28, figs. 4-6. 

 Hystrichosphaeridium inodes Klumpp ; Brosius : 40, pi. 5, fig. 5. 

 Cordosphaeridium inodes (Klumpp) Eisenack : 261, pi. 29, fig. 3. 



