AND CAINOZOIC DINOFLAGELLATE CYSTS " 7 



?Polysphaeridium rhabdophorum (Valensi) Davey & Williams, comb, nov., 



= Hystrichosphaeridium rhabdophorum Valensi, 1955b ; 593-4, pi. 3 fig. 7. 



Cretaceous, France. 

 }Polysphaeridium simplex (White) Davey & Williams, comb, nov., =Xanthidium 



tubiferum subsp. simplex White, 1842 ; 38-9, pi. 4 div. 3 fig. 10 (elevated to 



specific status, as Hystrichosphaeridium simplex, by Deflandre, 1946a ; card 



934). Upper Cretaceous, England. 

 }Polysphaeridium tribrachiosum (Tasch) Davey & Williams, comb, nov., 



= Hystrichosphaeridium tribrachiosum Tasch in Tasch, McClure & Oftedahl, 



1964 ; 195, pi. 1 fig. 3. Lower Cretaceous, Kansas, U.S.A. 

 IDiphyes monstruosum (Tasch) Davey & Williams, comb, nov., =Hystricho- 



sphaeridium monstruosum Tasch in Tasch, McClure & Oftedahl, 1964 ; 195, 



pi. 1 fig. 12. Lower Cretaceous, Kansas, U.S.A. 

 Tanyosphaeridium ellipticum (Cookson) Davey & Williams, comb, nov., 



= Hystrichosphaeridium ellipticum Cookson, 1965 ; 87-8, pi. 11 figs. i-3a. 



Upper Eocene, Australia. 

 Tanyosphaeridium isocalamus (Deflandre & Cookson) Davey & Williams, 



comb, nov., = Hystrichosphaeridium isocalamus Deflandre & Cookson, 1955 ; 



272, pi. 2 figs 7-8, text-figs 30-35. Lower Cretaceous, Australia. 



III. TAXONOMIC CHANGES PROPOSED BY W. A. S. SARJEANT 



In a recent publication, Wall (1967 ; 98) has discussed the difficulties encountered 

 in distinguishing between the genera Gonyaulacysta and Leptodinium. Hitherto this 

 had been done on the presence of a sixth precingular plate (numbered as plate 1'") 

 in the former genus — a feature frequently difficult to discern, even in the type 

 species, G. jurassica. Wall proceeded to formulate a revised diagnosis for the genus 

 Leptodinium, emphasizing the absence of apical or antapical structures and the 

 simplicity of the crests, which are typically low and lack spines or other outgrowths 

 (1967 ; 104). This diagnosis did not take account of the revisions in these two 

 genera proposed by Sarjeant (1966b ; 111, 113) ; and so revised diagnoses for the 

 genera Gonyaulacysta and Leptodinium, embodying ideas drawn from both sources, 

 are now given. Two species which fall outside the revised diagnoses of both genera 

 are placed into a new genus, here proposed. 



Genus GONYAULACYSTA Deflandre ex Norris & Sarjeant 1965 

 emend, Sarjeant, herein 



1964 Gonyaulacysta gen. nov. Deflandre : 5. [Type species not validly proposed : see 

 I. C.B.N. Art. 33 para. 4]. 



1965 Gonyaulacysta Deflandre ; Norris and Sarjeant : 65. [Type species validly proposed]. 



1966 Gonyaulacysta Deflandre ; Loeblich & Loeblich : 33. 

 1966b Gonyaulacysta Deflandre ; emend. Sarjeant : 111. 



1967 Gonyaulacysta Deflandre ; Wall : 98 (discussion only : no diagnosis given). 



