58 MESOZOIC AND CAINOZOIC DINOFLAGELLATE CYSTS 



Discussion. H. tiibiferum has been recorded many times but often incorrectly. 

 The specimens figured by Reade (1839, pi- 9> n S s - 6, 19) and Deflandre (1937, pi. 12, 

 fig. 14 ; pi. 13, figs. 2, 14) show all the characteristics of Hystrichosphaeridium 

 recurvation (White) and should be regarded as attributable to this species. H. 

 tubiferum (Valensi, 1955, pi. 4, fig. 2 ; pi. 5, fig. 8) may also belong to H. recurvatum. 



The specimens illustrated by Eisenack (1958, pi. 25, fig. 16) and Pocock (1962, pi. 

 15, fig. 230) should probably be referred to Oligosphaeridium complex (White). 



A number of other specimens have been referred to H. tubiferum but their true 

 systematic position is doubtful, and almost certainly they do not belong to this 

 species. 



Hystrichosphaeridium tubiferum (Ehrenberg) var. brevispinum nov. 



PL 10, fig. 10 



Derivation of name. Latin, brevis, short ; spina, spine — referring to the short 

 processes. 



Diagnosis. A variety of Hystrichosphaeridium tubiferum with processes rarely 

 exceeding one-third of the diameter of the central body. 



Holotype. B.M.(N.H.) slide ¥.51738(1). Metropolitan Water Board Borehole 

 No. 39, at 160 feet depth, London Clay ; Enborne, Berkshire. 



Dimensions. Holotype : diameter of central body 32 by 36^ ; length of 

 processes up to iiji. ; width of processes up to iijjl ; number of processes 23. 

 Range : diameter of central body 3i-53[x ; length of processes 6-1 ijx ; width of 

 processes up to I3[i. ; number of specimens measured, 7. 



Remarks. This variety forms a distinct group distinguishable from Hystri- 

 chosphaeridium tuberiferum only by the length of the processes. It differs from 

 ? Hystrichosphaeridium arundum (Eisenack & Cookson i960) from the Lower Creta- 

 ceous of Australia, by having much broader processes. 



Hystrichosphaeridium deanei sp. nov. 

 PL 6, figs. 4, 8 



Derivation of name. Named in honour of H. Deane, an early worker on fossil 

 microplankton from the Chalk of England. 



Diagnosis. Subspherical to ovoidal central body composed of thin smooth 

 endophragm and smooth or slightly granular periphragm, the latter forming the 

 processes. Tubular processes varying considerably in shape, sub-conical, lagenate 

 or tubiform, open distally with entire or serrate margins. Width of processes 

 extremely variable. Apical archaeopyle usually present. 



Holotype. Geol. Surv. Colin, slide PF. 3030(1). Lower Chalk, H.M. Geological 

 Survey Borehole, Fetcham Mill, Surrey, at 690 feet depth. Upper Cretaceous 

 (Cenomanian). 



