STUDIES ON MESOZOIC AND CAINOZOIC 

 DINOFLAGELLATE CYSTS 



By R. J. DAVEY, C. DOWNIE, 

 W. A. S. SARJEANT & G. L. WILLIAMS 



CONTENTS 



I. Introduction . . . . • 



II. The morphology, terminology and classification of fossil 

 dinoflagellate cysts (C. Downie & W. A. S. Sarjeant) 

 Morphology and terminology 

 Classification ..... 



III. Stratigraphy and historical background 



a. The Speeton Clay (W. A. S. Sarjeant) 



b. The Lower Chalk (R. J. Davey) 



c. The London Clay (G. L. Williams & C. Downie) 



IV. The genera HYSTRICHOSPHAERA and ACHOMOSPHAERA 



(R. J. Davey & G. L. Williams) . 



Introduction ..... 

 Genus Hystrichosphaera O. Wetzel 

 Hystrichosphaera ramosa (Ehrenberg) 

 var. ramosa nov. . 

 gracilis nov. . 

 granosa nov. 

 multibrevis nov. 

 membranacea (Rossignol) 

 granomembranacea nov. 

 reticulata nov. 

 cingulata (O. Wetzel) 

 var. reticulata nov. 

 crassimurata sp. n. 

 crassipellis Deflandre & Cookson 

 perforata sp. n. 

 buccina sp. n. 

 cornuta Gerlach 

 var. laevimura nov. 

 cf. cornuta Gerlach 

 monilis sp. n. 

 sp. . 

 Genus Achomosphaera Evitt 



Achofnosphaera ramulifera (Deflandre) 

 var. perforata nov. . 

 alcicornu (Eisenack) 

 sagena sp. n. . 

 neptuni (Eisenack) . 

 Other Species .... 



Conclusions ..... 

 V. The genus HYSTRICHOSPHAERIDIUM and its allies (R. J 

 Davey & G. L. Williams) 



Introduction ..... 

 Genus Hystrichosphaeridium Deflandre 



Hystrichosphaeridium tubiferum (Ehrenberg) 

 var. brevispinum nov. 



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