MESOZOIC AND CAINOZOIC DINOFLAGELLATE CYSTS 193 



The processes vary in width from 1-5-3^ ; they are in contact with the pericoel 

 and are distally open, their margins being aculeate, with up to six aculei arising from 

 a single process. The length of the aculei can be as great as 7jjl ; in some specimens 

 they are granular. The nature of the processes distally is one of the diagnostic 

 features of specimens of W. ovalis from the London Clay. 



The capsule almost completely fills the pericoel, sometimes even exhibiting a 

 protuberance when opposite a horn. Its wall can be smooth or granular. An 

 archaeopyle is commonly present. 



Dimensions. Range observed in London Clay : outer shell — length 94-120^, 

 breadth jj-ii$[l. Capsule — length 68-79(1., breadth 67-78^. Number of specimens 

 measured, 7. 



Occurrence. Eocene, London Clay ; Whitecliff and Enborne. 



Stratigraphic range. Present in the Oligocene of Germany (Eisenack 1954&) 

 and in the London Clay. 



Wetzeliella (Wetzeliella) condylos sp. nov. 

 PL 20, figs. 1, 2 



Derivation of name. Greek, kondylos, knuckle, knob, enlarged end of a bone : 

 referring to the form of the processes. 



Diagnosis. Flattened outer shell with well formed lateral horns, low or absent 

 apical horns and two antapical horns, the right one always longer. Apical area 

 tending to be curved. Periphragm ornamented with a number of extremely short, 

 blunt intratabular processes some arranged in simulate complexes reflecting a tabula- 

 tion of 4', 3a, 7", xc, 5'", 2"", 3s, others occurring within complexes. Hypotract of 

 periphagm of greater length than epitract. Capsule ovoidal to sub-circular in outline 

 ellipsoidal in cross section. Endophragm up to yS\i thick, surface smooth or 

 undulating. 



Holotype. B.M.(N.H.) slide V. 51967. London Clay ; Sheppey, Kent, sample 

 Sh.2. 



Dimensions. Holotype : Periphragm, length i22[x, breadth ii2-5[x. Observed 

 range : outer shell, length 76-i22[x, breadth 86-115^.. Capsule, length 56-85^ ; 

 breadth 62-85^. Number of specimens measured, 6. 



Description. The periphragm of W. condylos is up to 3[x thick and forms the 

 extremely small processes. These open to the pericoel and are cylindrical in cross 

 section and distally closed with a blunt ending. The height of the processes is of the 

 order of i-3[a. The characteristic generic tabulation can be determined from the 

 regular disposition of the processes in simulate complexes on the pericoel. Auxiliary 

 irregularly arranged processes are also common. The lateral horns of the peri- 

 phragm are always prominently developed ; the apical horn, if present, is at the 

 most a small protuberance. The capsule occasionally abutts on to the inner surface 

 of the periphragm. 



