120 MESOZOIC AND CAINOZOIC DINOFLAGELLATE CYSTS 



Paratype. B.M.(N.H.) slide V.5i73o(5). Same locality and horizon. 



Dimensions. Holotype : overall length 151(1, breadth ny\i. Shell length 

 117(1 ; length of horn 34^ ; breadth of cingulum c.yy.. Paratype : overall length 

 145^, breadth c.i I2[x ; shell length 105^ ; length of horn 40^ ; breadth of cingulum 

 c.5fx. Range : overall length 0.140-155(1. 



Description. This is an unusually large and very characteristic species, quite 

 frequent at this horizon, some 20 specimens having been studied. The dense 

 granulation and relatively inconspicuous character of the crests render the tabulation 

 difficult to determine : Text-fig. 28 was prepared from study of several specimens 

 and is unlikely to be accurate in detail. On most specimens, including the holotype, 

 granules are absent from various small patches of the surface : this appears to 

 result from damage. Granulation is consistently faint or lacking on the sulcus, 

 which is somewhat sunken. 



The test is spherical to spheroidal and composed of two distinct layers ; a fairly 

 thin periphragm and a thicker endophragm. The endophragm bulges only into the 

 base of the apical horn, so that the horn contains a cavity between the wall layers. 



Fig. 28. Gonyaulacysta hadra sp. nov. Tabulation. Left, ventral view ; right, dorsal 

 view. Insert : the wall structure at the apex, in diagrammatic section. x c. 550. 



