70 MESOZOIC AND CAINOZOIC DINOFLAGELLATE CYSTS 



considerably and may measure up to iOfj. at their contact with the central body and 

 often show noticeable basal wrinkles. An apical archaeopyle always appears to be 

 present. The tabulation reflected by the processes is : (4'), 6", 6c, 5'", ip, 1"" and 

 about 5s. 



Remarks. H. bowerbanki sp. nov. differs from H. recurvatum (White) in being 

 smaller and having wider tubular processes. It is rather similar to H. sheppeyense 

 but the form of the central body is more elongate ; the processes are wider, especially 

 at their base, and have a much thinner wall. 



OTHER SPECIES 



The following species are here attributed to the genus Hystrichosphaeridium 

 emend, on the basis of the number of processes and general form : 



Hystrichosphaeridium cf. clavigerum (Deflandre) ; Lejeune-Carpentier 1940. 

 Upper Cretaceous ; Belgium. 



Hystrichosphaeridium irregulare (Merrill 1895). Lower Cretaceous ; U.S.A. 



Hystrichosphaeridium stellatum (Maier 1959). Oligocene ; Germany. 



The following described species are doubtfully included in Hystrichosphaeridium 

 emend, on the basis of the number and form of processes present : 



? Hystrichosphaeridium arundum (Eisenack & Cookson i960). Upper Cretaceous ; 

 Australia. 



? Hystrichosphaeridium aquitanicum (Deunff 1961). Lower-Upper Cretaceous ; 

 France. 



? Hystrichosphaeridium gliwicense (Macko 1957). Miocene ; Poland. 



? 'Hystrichosphaeridium hilli (Merrill 1895). Lower Cretaceous ; U.S.A. 



? Hystrichosphaeridium polyplasium (Maier 1959). Miocene ; Germany. 



Hystrichosphaeridium claviferum (Wilkinson 1849) '> Deflandre 1946a (incorrectly 

 transferred to Baltisphaeridium by Downie & Sarjeant 1963) and Hystrichosphaeri- 

 cruciatum O. Wetzel 1933 from the description and figures both appear to be the 

 detached apical regions of species of Hystrichosphaeridium emend., bearing four 

 processes. The holotype of H. clavigerum is lost ; it appears likely that it represents 

 the apical region of H. tubiferum, of which the species H. clavigerum may be regarded as 

 a junior synonym and should therefore be rejected. H. cruciatum, as illustrated 

 by Lejeune-Carpentier (1940, fig. 14), represents the apical region of an otherwise 

 undescribed species. 



Genus OLIGOSPHAERIDIUM nov. 



Derivation of name. Greek, oligo, few or scanty ; sphaera, ball — with reference 

 to the ball-like central body bearing a small number of processes. 



