MESOZOIC AND CAINOZOIC DINOFLAGELLATE CYSTS 73 



0. complex thus has a stratigraphic range from the Neocomian (Gocht 1959 and 

 Cookson & Eisenack 1958) to the Ypresian. 



Remarks. Oligosphaeridium complex was first described by White (1842) as 

 Xanthidium tubiferum complex. In the description of the processes White stated : 

 " Sometimes the orifice is separated into unequal divisions of four, five and six parts, 

 in others like one variety of X. ramosum before noticed ; the branching terminations 

 are of a more complex structure, each branch having at its extremes a further 

 ramification ; at which last I am inclined not to consider a variety of one species, 

 but the same as the former, in an advanced state of development. " Lejeune- 

 Carpentier (1940) briefly described forms having distal prolongations under Hystri- 

 chosphaeridium elegantulum. These she compared to X. tubiferum complex (White) 

 and concluded that they were identical. In White's figures branching is clearly 

 shown ; Lejeune-Carpentier's figures 11 and 12, however, suggest that some at 

 least of the so-called distal branchings of the processes are bifurcating secae of simple 

 processes. H. elegantulum was transferred to H. complex by Deflandre (1946) on the 

 grounds that it was an invalid synonym, but no new diagnosis was given for H. 

 complex. Firtion (1952) figured different process terminations for the species. 

 These cannot be seen in his indistinct plates and in his description he simply states 

 " . . . . the shell is furnished with tubiform radiating appendages ; their distal 

 extremity very splayed-out, showing a system of fine and deep dentations." 



H. tubiferum (Cookson 1953, pi. 2, fig. 24) later placed in H. complex (Deflandre & 

 Cookson 1955) is of doubtful status. 



Valensi (1955) figured H. complex, branching in at least four processes. In the 

 same year, Deflandre & Cookson enlarged the concept of this species by including 

 within it specimens having cathrate extremities, transitional to H. pulcherrimum. 

 Their figures closely approach the London Clay forms. Cookson & Eisenack (1958) 

 figured H. complex with simple processes developed distally into aculei. Eisenack 

 (1958) Gocht (1959) and Cookson & Hughes (1964) figured specimens with simple 

 unbranched processes, produced distally into aculei. 



Neale & Sarjeant (1962) in discussing their new species H. macrotubulum decided 

 that forms possessing unbranched processes did not belong to H. complex. Partly 

 on this basis, partly on the granular nature of the central body, they separated 

 H. macrotubulum as a distinct species. In view of the uncertainty concerning the 

 degree of branching of the processes, both branched and simple forms have been 

 included in H. complex. 



Much more significant is the tabulation inferred from the positions of the processes. 

 The specimens of H. complex illustrated by Firtion (1952), Deflandre & Cookson 

 (1955), Cookson & Eisenack (1958) and Gocht (1959) are clearly forms lacking 

 cingulum processes and possessing an apical archaeopyle. 



As Deflandre & Cookson (1955) noted, transitional forms to H. pulcherrimum 

 occur, which have perforate processes ; the perforations are not, however, excessively 

 numerous and for this reason the specimens concerned were placed in H. complex. 

 Comparable forms have been observed in the Cenomanian of England. 



