MESOZOIC AND CAINOZOIC DINOFLAGELLATE CYSTS 91 



throughout their length. There are 18 to 20 processes, an apical archaeopyle 

 usually being present. The shape and form of the archaeopyle is difficult to deter- 

 mine and a detached apical region has not, as yet, been observed. However the 

 archaeopyle is thought to be haplotabular and the spines to have an inferred reflected 

 tabulation of 1', 6", 6c, 5'", 1"" and o-2s. 



?C. fasciatum sp. nov. has only been recorded from the Lower Barremian of 

 Yorkshire. 



Remarks. The short, wide tabular processes differentiate this species from 

 ?C. eoinodes (Eisenack) and the nature of the periphragm on the central body is 

 probably different although this was not commented on in the original diagnosis or 

 description. The nature of the periphragm on the surface of the central body and 

 when composing the processes of Hystrichosphaeridium radiculum sp. nov. and 

 H. mantelli sp. nov. is very similar to C. fasciatum perhaps indicating a relationship 

 between the three species. Each form possesses a distinctive type of process and the 

 two forms of Hystrichosphaeridium have a greater number of processes than does 

 C. fasciatum. The type of archaeopyle is a very important factor in determining 

 the above relationships but unfortunately the exact type of archaeopyle has not 

 been determined as yet. 



?C. fasciatum is thought to belong to Cordosphaeridium on account of the probable 

 presence of a haplotabular archaeopyle, the number of processes and the fibrous 

 nature of the periphragm so commonly observed in species of this genus. 



OTHER SPECIES 



The following species are here tentatively referred to the genus Cordosphaeridium 

 Eisenack 1963, emend, on the basis of the number and type of processes: 



? Cordosphaeridium cantharellum (Brosius 1963). Oligocene ; Germany. 



? Cordosphaeridium difficile (Manum & Cookson 1964). Upper Cretaceous ; 



Arctic Canada. 

 1 Cordosphaeridium diktyoplokus (Klumpp 1953). Eocene ; Germany. 

 ? 'Cordosphaeridium diktyoplokus subsp. latum (Klumpp 1953). Eocene; Germany. 

 1 Cordosphaeridium eoinodes (Eisenack 1958). Lower Cretaceous ; Germany. 

 7 Cordosphaeridium erectum (Manum & Cookson 1964). Upper Cretaceous ; 



Canada. 

 ? Cordosphaeridium floripes (Deflandre & Cookson 1955). Miocene ; Australia. 

 ? Cordosphaeridium floripes subsp. breviradiatum (Cookson & Eisenack 1961). 



Eocene ; Australia. 

 } Cordosphaeridium microtriaina (Klumpp 1953). Eocene ; Germany. 



Genus POLYSPHAERIDIUM nov. 



Derivation of name. Greek, polys, many ; sphaero, ball — with reference to the 

 central spherical body which bears numerous processes. 



Diagnosis. Chorate cysts possessing sub-spherical to ovoidal central body and 

 bearing numerous processes all similar in size. Number of processes per plate area 



