MESOZOIC AND CAINOZOIC DINOFLAGELLATE CYSTS 97 



Remarks. The diagnosis of Diphyes has been emended to relate the process 

 arrangement to a dinoflagellate tabulation, and to draw attention to the single 

 antapical process. 



In the original diagnosis, the smaller processes are said to be closed. The figure 

 by Deflandre & Cookson (1955, pi. 7, fig. 3) seems to indicate, however, that the 

 processes are open, as in the examples from the London Clay. Cookson & Eisenack 

 (1961, pi. 2, fig. 9) figured H. colligerum with the processes definitely open. The 

 species may well be confined to examples with open processes after re-examination 

 of the holotype. Cookson (1965, pi. 9, figs. 1-3) illustrates forms with distinctively 

 larger antapical processes not unlike those of Litosphaeridium siphoniphorwm 

 (Cookson & Eisenack) . Because of the larger size of this process she has incorrectly 

 considered it to represent a second portion of the central body and has erected a new 

 genus diagnosed as possessing bipartite cysts. The forms from the London Clay, 

 the holotype of D. colligerum and the specimen illustrated by Cookson & Eisenack 

 (196 1, pi. 2, fig. 9) are probably more typical of the species and show without doubt 

 that the " posterior portion of the shell " is in fact an enlarged antapical process. 

 This species has been recorded from the Upper Cretaceous (probably Senonian) and 

 Eocene of Australia, and in England only from the Eocene. 



This species is easily distinguishable from all other types of dinoflagellate cysts. 



OTHER SPECIES 



The following species is here tentatively referred to the genus Diphyes on the basis 

 of the numerous processes and single distinctive antapical process : 



? Diphyes monslruosum (Tasch, McClure & Oftedahl 1964). Lower Cretaceous ; 

 U.S.A. 



Genus DUOSPHAERIDIUM nov. 



Derivation of name. Latin, duo, two ; sphaera, ball — with reference to 

 the biospheroidal form of the test. 



Diagnosis. Proximate cyst composed of two more or less spheroidal parts, 

 neither bearing processes. Anterior part with apical archaeopyle. Posterior part 

 similar in shape with small circular antapical opening present. 



Type species. Diphyes nudum Cookson 1965. Upper Eocene ; Australia. 



Remarks. The type species was formerly placed in the genus Diphyes by Cookson 

 (1965) because of the apparent resemblance of its posterior part to the antapical 

 process of Diphyes colligerum. However, the latter is a chorate cyst whereas the 

 former is proximate, a difference considered by the authors to be of profound 

 significance in the development history of dinoflagellate cysts and thus to preclude 

 classification in the same genus. 



