136 MESOZOIC AND CAINOZOIC DINOFLAGELLATE CYSTS 



Leptodinium membranigerum Gerlach 1961. Oligocene ; Germany. 



Leptodinium mirabile Klement 1960. Upper Jurassic (?Oxfordian-Lower 

 Kimmeridgian) ; Germany. 



? Leptodinium tenuicornutum Cookson & Eisenack 1962&. Cretaceous (PAlbian) ; 

 Western Australia. 



Genus RAPHIDODINIUM Deflandre 1936 : 184 



Type species. Raphidodinhim fucatuni Deflandre 1936. Upper Cretaceous ; 

 France. 



Remarks. This genus comprises highly condensed proximo-chorate cysts of 

 ovoidal shape, characterized by possession of a very few extremely long spines, 

 about 12 in number and up to twice the shell length. The shell surface bears low 

 crests outlining a tabulation : the spines arise from crest nodes. The tabulation 

 has not been determined, nor has an archaeopyle been reported ; the systematic 

 position thus remains obscure. It is clearly a cyst genus, however, since spines 

 arise from the cingulum. 



Genus PSALIGONYA ULAX nov. 



Derivation of name. Greek, psalis, low building with a vaulted roof ; a 

 variant of the Gonyaulax tabulation type with terminal pericoels. 



Diagnosis. Bicavate dinoflagellate cysts, pericoel separated into two portions by 

 broad median zone of contact with inner body. Outline spheroidal to ellipsoidal or 

 subpolygonal with apical horn. Tabulation 3-4', ia, 6", 6c, 6'", ip, 1"" determinable 

 on periphragm, sutures in form of ridges of varied height and ornament. No spines 

 arise from crest nodes. Surface of endophragm and periphragm smooth, granular, 

 nodose, reticulate or punctate. Precingular archaeopyle formed by loss of plate 3". 



Type species. Psaligonyaulax deflandrei sp. nov. Upper Cretaceous (Ceno- 

 manian) ; England. 



Remarks. This new genus is distinguished from Gonyaulacysta by the presence 

 of apical and antapical pericoels ; the species Gonyaulacysta cassidata, which has a 

 closely similar tabulation pattern to that of the type species of Psaligonyaulax and 

 which has an apical pericoel but no antapical pericoel, may well represent an inter- 

 mediate form. 



Psaligonyaulax is distinguished from Scriniodinium sensu stricto by the separation 

 of the pericoel into two parts ; from the subgenus Scriniodinium by the presence of a 

 clear tabulation ; from the subgenus Endoscrinium by possession of a posterior 

 intercalary plate and an antapical plate. 



