206 MKSOZOIC AND CAINOZOIC DINOFLAGELLATE CYSTS 



with short spines, simple or bifurcate : arrangement is in general random, but 

 sometimes in rows, suggesting traces of tabulation. Equatorial zone, corresponding 

 to cingulum, lacking spines : not hollowed. No pattern of sutures visible, no clear 

 indication of sulcus. Apical archaeopyle formed by schism of shell on angular line 

 of breakage. 



Type species. Doidyx anaphrissa sp. now Lower Cretaceous (Lower Barre- 

 mian) ; England. 



Remarks. In its asymmetrically biconical shell, spine cover and absence of 

 tabulation, this new genus differs from all described fossil genera. The asymmetry 

 and mode of archaeopyle formation suggests a probable derivation from the genus 

 Pseitdoceratium by reduction of polar horns and loss of the lateral horn. 



Doidyx differs from Diconodinium, Palaeohystrichophora and Dioxya in its asym- 

 metrical shape : from Diconodinium also in the absence of a sulcus : from Palaeo- 

 hystrichophora also in the lack of an inner body ; and from Dioxya in the clear 

 indication of a cingulum. It differs from the superficially similar genus Aptea in the 

 lack of an enclosing membrane. 



Doidyx anaphrissa sp. nov. 

 PL 22, fig. 8 ; PI. 23, fig. 6 ; Text-fig. 55 



Derivation of name. Greek, anaphrisso, to bristle. 



Diagnosis. A Doidyx having an asymmetrically biconical shell with short, 

 blunt apical horn and with low bump on antapex. Spines simple, capitate or briefly 

 bifurcate. Portion thrown off in archaeopyle formation exceeding one-third of shell 

 length. 



Fig. 55. Doidyx anaphrissa sp. nov. Holotype, 

 showing archaeopyle formation. x c. 750. 



