->io MESOZOIC AND CAINOZOIC DINOFLAGELLATE CYSTS 



Gardodiniutn eisenacki Alberti 



PI. 21, fig. 4 



1961. Gardodinium eisenacki Alberti : 18, pi. 3, figs. 8-13. 



Remarks. This species occurs in moderate abundance in the assemblages from 

 39 metres and 42-5 metres depth. Specimens are frequently distorted. The 

 figured specimen, B.M.(N.H.) slide ¥.51726(1), is the best preserved ; its dimensions 

 are overall length j6\x, breadth 55^ ; shell length 56(0., breadth 50;x. The range of 

 dimensions exhibited accords closely with that quoted by Alberti (77-85(0 x 55-60(0 

 overall). 



Genus DINGODINIUM Cookson & Eisenack 1958 : 39 



Type species. Dingodinium jurassicum Cookson & Eisenack 1958. Upper 

 Jurassic ; Papua and Australia. 



} Dingodinium albertii sp. nov. 



PL 21, fig. 3, PL 23, fig. 1 



1961. Dingodinium sp. A., Alberti : 17, pi. 3, fig. 16. 



Derivation of name. Named in honour of Dr. Gerhard Alberti, the first to 

 describe this form of cyst. 



Diagnosis. A cavate dinoflagellate cyst with thin outer shell, irregularly ovoidal 

 to subpolygonal in outline, drawn out into a blunt, stout apical horn ; inner body 

 thin, spheroidal, with dense cover of large, pointed tubercles. Outer shell posses- 

 sing clear helicoid cingulum marked by prominent folds or ridges ; further folds or 

 ridges, less prominent, define tabulation. Intercalary archaeopyle apparently 

 formed. 



Holotype. B.M.(N.H.) slide ¥.51719(2). Speeton Clay, Shell West Heslerton 

 boring at 42-50 metres depth, West Heslerton, Yorks. Lower Cretaceous (Lower 

 Barremian). 



Paratype. B.M.(N.LL) slide ¥.51723(1). Same locality and horizon. 



Dimensions. Holotype — overall length 66[i, breadth 52^, length of inner body 

 40jjl, breadth 45^. Paratype — overall length 57(0, breadth 48^, length of inner body 

 37(jl, breadth 39(0. Range of dimensions — overall lengths 50-66(1, breadths 37- 5—52(0.. 



Description. The outer shell is basically ovoidal to polygonal ; but it is 

 extremely thin and is deformed in variable fashion in the seven specimens examined. 

 It bears folds or ridges which simulate a tabulation and is drawn out into a short 

 apical horn with a blunt, slightly rounded tip. The inner body is spheroidal and 

 typically broader than long. The periphragm is smooth ; the endophragm smooth 

 or very minutely granular. The latter bears a moderately dense cover of tubercles ; 

 these are conical and do not exceed i[x in height. There is some suggestion that the 

 tubercles show a degree of alignment, but this could not be confirmed. 



