196 MESOZOIC AND CAINOZOIC DINOFLAGELLATE CYSTS 



Wetzeliella (Wetzeliella) symmetrica Weiler 



PI. 20, fig. 6 



1956. Wetzeliella symmetrica Weiler : 132, pi. 11, figs. 1-3 ; text-figs. 2-5. 

 1963. Wetzeliella symmetrica Weiler ; Brosius, pi. 2, fig. 7. 



Discussion. This species is characterized by a periphragm with rhomboidal 

 outline, the angles of which are prolonged into more or less equally long horns. The 

 single antapical horn sits astride the mid-ventral line. The processes commonly 

 have aculeate distal margins or can be bifurcate. 



Dimensions. Range observed in London Clay : outer shell, length 125-167^, 

 breadth n.5-148^. Capsule, length 70-97^, breadth 66-88[x. Number of speci- 

 mens measured, 7. 



Occurrence. Eocene, London Clay ; Whitecliff, Enborne, Studland and Shep- 

 pey. Wetzeliella (W .) symmetrica has also been recorded from the Oligocene of 

 Germany (Weiler 1956, Alberti 1961, Gerlach 1961 and Brosius 1963). 



Wetzeliella (Wetzeliella) symmetrica var. lobisca nov. 

 PI. 20, fig. 3 



1948. Hystrichosphaeridium articulatum Pastiels : 43, pi. 4, figs. 13, 17. 

 1961. Wetzeliella symmetrica symmetrica Gerlach : 185, pi. 25, figs. 7, 8. 



Derivation of name. Latin ; lobisca, a small protuberance. 



Holotype. B.M.(N.H.) slide V.51970. London Clay ; Sheppey, Kent, sample 

 1. 



Dimensions. Holotype : outer shell, length 13711, breadth I23fx. Capsule, length 

 j8[i, breadth yo\x. Observed range : outer shell, length I25-I37fi., breadth, 118- 

 I50pt. Capsule, length 72-80^, breadth 70-79^. Number of specimen, measured, 4. 



Description. This is a variety of W. (W.) symmetrica which has a slightly 

 reduced apical horn and the single antapical horn is offset to the right of the mid- 

 ventral line. It is identical with the two figured specimens of W. symmetrica 

 symmetrica Gerlach (1961) and Hystrichosphaeridium articulatum Pastiels (1948). 



Occurrence. Eocene, London Clay ; Whitecliff, Enborne and Sheppey. It has 

 also been recorded from the Ypresian of Belgium (Pastiels 1948 as H. articulatum) 

 and the Oligocene-Miocene of Germany (Gerlach 1961). 



Wetzeliella (Wetzeliella) varielongituda sp. nov. 

 PI. 20, figs. 4, 8 



Derivation of name. Latin ; varius, varied, longituda, length. 



Diagnosis. Periphragm outline sub-rhomboidal, with short broad lateral horns, 

 a short wide apical horn and one well developed (right) antapical horn. Left 



