212 MKSOZOIC AND CAINOZOIC DINOFL AGELL ATE CYSTS 



indigenous. P. ceratophora thus emerges as having a known range from Callovian to 

 Barremian. The shape and dimensions of the Speeton specimens accord with the 

 range quoted by Deflandre as typical (overall length 65-78^), the figured specimen, 

 B.M.(N.H.) slide ¥.51724(4), having an overall length of 71^, with apical horn 

 I3"5(x long, and a breadth of S7'5V- 



Genus SIRMIODINI UM Alberti 1961 : 22 



Type species. 5. grossi Alberti 1961. Lower Cretaceous (U. Hauterivian-U. 

 Barremian) ; Germany. 



Sirmiodinium grossi Alberti 

 PL 22, fig. 7 



1961. Sirmiodinium grossi Alberti : 22, pi. 7, figs. 5-7, pi. 12, fig. 5. 



Remarks. This species is represented in four studied horizons of the Speeton 

 Clay, at 39-0, 42-5, 99-25 and 103-25 metres depth. (Middle Hauterivian to Lower 

 Barremian.) The range of dimensions exhibited is similar to, but somewhat greater 

 than, that quoted by Alberti (overall length 87-92^, breadth 8i-85[x) ; the figured 

 specimen, B.M.(N.H.) slide ¥.51722(2), having the dimensions overall length 95^, 

 breadth 8^\i, length of inner body 65^, breadth 63^.. 



Genus COMETODINIUM Deflandre & Courteville 1939 : 98 



Type species. C. obscurum Deflandre & Courteville 1939. U. Cretaceous ; 

 France. 



Cometodinium sp. 



PI. 22, fig. 6 



Description. Shell spherical to spheroidal, minutely granular, densely covered 

 by a mat of undulose hairlike spines. The spine-cover is lacking only in a narrow 

 median belt corresponding to the cingulum ; this may be partly or wholly obscured 

 from view, by the tangled spines. Archaeopyle not seen. 



Figured specimen. B.M.(N.H.) slide ¥.51723(2), Speeton Clay, Shell West 

 Heslerton Borehole at 42-5 metres depth, West Heslerton, Yorks. Lower Cretaceous 

 (Lower Barremian). 



Dimensions. Figured specimen : overall length 62jx, breadth 68jx, shell length 

 37[x, breadth 44^, length of spines around i$\i.. Dimensions of other specimens 

 closely similar. 



Remarks. This form has been encountered only at one horizon, in low numbers. 

 It differs from Cometodinium obscurum in the lack of ridges edging the furrow ; the 

 absence of any indication of a sulcus ; and the considerably shorter spines. It is 

 perhaps more closely comparable to Baltisphaeridium whitei (Deflandre & Courteville 

 1939), also from the Cretaceous of France ; this latter species lacks any trace of a 



