MESOZOIC AND CAINOZOIC DINOFLAGELLATE CYSTS 183 



Sub-genus Wetzelliella (Wetzelliella) Eisenack 1938. 



Diagnosis. A sub-genus of the genus Wetzeliella, possessing numerous processes 

 developed from the periphragm. Processes showing only moderate variation in 

 length and may be united distally. Processes intratabular, forming simulate 

 complexes, or haphazardly distributed on plate. 



Type species. Wetzeliella [Wetzeliella) articulata Eisenack 1938. 



Wetzeliella (Wetzeliella) articulata Eisenack 

 PI. 18, figs. 1-4 



1935. Peridinium sp., O. Wetzel : 168, pi. 2, fig. 1. 



1938. Wetzeliella articulata Eisenack 



1950. Wetzeliella articulata Eisenack 



1952. Wetzeliella articulata Eisenack 



1952. Wetzeliella articulata Eisenack 



I 953- Wetzeliella articulata Eisenack 



1954. Wetzeliella articulata Eisenack 



1956. Wetzeliella articulata Eisenack 



1959a. Wetzeliella articulata Eisenack 



1 961. Wetzeliella articulata Eisenack 



1 961. Wetzeliella articulata Eisenack 



186, text-fig. 4. 



Reissinger : 119, pi. 19, fig. 6. 



Gocht : 314, pi. 2, figs. 38, 39. 



Deflandre, text-fig. 89. 



Klumpp : 393, pi. 19. figs. 1-5. 



Eisenack : 55, pi. 7, figs. 1-11 ; pi. 8, figs. 14-16. 



Cookson : 185, pi. 2, fig. 6. 



Eisenack, pi. 3, fig. 7. 



Evitt : 397, pi. 8, figs. 3, 5, 6. 



Gerlach : 152, pi. 25, fig. 2. 



Discussion. W. (W) articulata is of widespread occurrence in the London Clay 

 of Enborne and Sheppey but is uncommon at Whitecliff. The London Clay speci- 

 mens do not vary from the type material. The tabulation has beeen worked out in a 

 few individuals, from the alignment of some of the intratabular processes in simulate 

 complexes. These are four apicals, three anterior intercalaries (of which plates ia 

 and 3a are elongate) ; seven precingulars (with plates 2" and 6" elongate) ; 5 post- 

 cingulars (all well developed plates) ; two antapicals of approximately equal size 

 and three sulcals, with the posterior sulcal plate the largest. That the endophragm 

 is subdivided into plates of similar orientation is suggested by the regularly ortho- 

 gonal outline of the inner archaeopyle. 



Of the two antapical horns always present in W. (W) articulata the longer invari- 

 ably lies to the right of the mid- ventral line, (for definition see Evitt 1963). The 

 processes forming the simulate complexes lie just in from the plate boundaries. A 

 few of the London Clay specimens have granular processes. Beautifully formed 

 crystals of pyrite are found in the horns of some specimens but only rarely in the 

 endocoel. 



Specimens intermediate to Wetzeliella symmetrica Weiler (1956) from the Oligo- 

 cene of Germany, are not uncommon in the London Clay. These possess a reduced 

 left antapical horn and/or an elongate apical horn, a length/breadth ratio of approxi- 

 mately 1 to 1 and are probably synonymous with W. cf. symmetrica (Weiler) Maier 

 (1959). Gerlach (1961) in a discussion of W. symmetrica symmetrica Weiler, 

 mentions the occurrence of specimens with a second antapical horn. Unfortunately 

 she did not figure any such types. 



