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MESOZOIC AND CAINOZOIC DINOFLAGELLATE CYSTS 



Type species. Hystrichosphaeridium siphoniphorum Cookson & Eisenack 1958. 

 Probably Lower Cretaceous (Albian) ; Australia. 



Remarks. The presence of three apical processes and the absence of cingular 

 processes is diagnostic of this genus, and makes it easily recognizable. The sulcal 

 processes may be either absent or few. 



Litosphaeridium siphoniphorum (Cookson & Eisenack) 

 PI. 7, figs. 7, 8 ; Text-figs. 16, 17 



1958. Hystrichosphaeridium siphoniphorum Cookson & Eisenack : 44, pi. 11, figs. 8-10. 



1963. Hystrichokolpoma sp. B., Baltes : 587, pi. 6, figs. 6-8. 



1963. Hystrichokolpoma sp. A., Baltes : 587, pi. 6, figs. 1-5. 



1964. Hystrichosphaeridium siphoniphorum Cookson & Eisenack ; Cookson & Hughes : 48, 



pi. 9, fig- 15- 



Emended diagnosis. Spherical to sub-spherical central body composed of thin 

 endophragm and thick reticulate periphragm. Processes, composed of smooth 

 periphragm, varying considerably in shape and size but commonly cylindrical or 

 sub-conical and always hollow. Distal margin of processes entire or serrate. 

 Hexagonal apical archaeopyle usually present. Number of processes 13, rarely 14 

 or 15, in specimen possessing an archaeopyle. Inferred tabulation 3', 6", 5'", ip, 

 1"" and o-2s. 



Holotype. National Museum of Victoria, Australia, specimen no. P17468, from 

 Gingin Area, W.A., Seismic shot hole B2 at 230 ft. Horizon — probably Albian. 



Dimensions. Holotype : overall diameter 76^, diameter of central body 43^, 

 length of processes c. ig-24[x. Paratype : overall diameter 69(0., diameter of central 

 body 33[x, length of processes c. 14^., operculum width 21\l. 



Fig. 16. Litosphaeridium siphoniphorum (Cookson & Eisenack). A specimen from the 

 Cenomanian. Left, apical view, showing the six-sided archaeopyle and the arrangement 

 of the processes ; right, antapical view. x c. 450. 



