MESOZOIC AND CAINOZOIC DINOFLAGELLATE CYSTS 191 



The processes of specimens of W. homomorpha from the London Clay are variable, 

 simple or branched, single or in linear complexes, distally bifid, blunt or acuminate 

 or with restricted opening. When open the processes have an entire margin. It is 

 impossible to distinguish varieties of W. homomorpha on types of processes, since 

 different types are often found on the same individual. The tabulation agrees with 

 that for the genus, some of the processes closely following the plate boundary and 

 almost being on it, others being well in from the margins. The number of processes 

 per plate is variable. The lateral, apical and antapical areas can be marked by 

 broad multibranched processes. 



Included within W. homomorpha are some of the forms described by Pastiels (1948) 

 as Hystrichosphaeridium geometricum. Fuller discussion of the W. homomorpha/ 

 H. geometricum complex will be found under W. homomorpha var. quinquelata. 



Wetzeliella (Wetzeliella) homomorpha var. quinquelata nov. 



PL 18, fig. 7 



1948. Hystrichosphaeridium geometricum Pastiels (pars) : 41, pi. 14, figs. 1, 2, 4, 8, 11. 

 1961. Wetzeliella cf. oralis Eisenack ; Alberti : pi. 1, fig. 13. 



Derivation of name. Latin, quinque, five ; latus, side — hence, five-sided. 



Holotype. B.M.(N.H.) slide ¥.51963(1). London Clay ; Whitecliff, sample 

 WC4. 



Dimensions. Holotype : periphragm, length 94[x ; breadth io5jx. Capsule, 

 length 69^ ; breadth 69^. Observed range : outer shell, length (including horns 

 and processes) 73—94(0., length (excluding horns and processes) 50-72^, breadth 

 (including horns and processes) yy-io^\i, breadth (excluding horns and processes) 

 53-70P1. Capsule, length 47-69^ ; breadth 50-69^. Length of processes 7. 

 Number of specimens measured, 7. 



Description. This is a variety of W. homomorpha having a thin periphragm with 

 a distinctly pentagonal outline. Each angle of the periphragm may be marked by a 

 branched process, larger than the rest, or by a horn not exceeding 20(j, in length. 

 When two antapical horns are present, the right is invariably the longer. The 

 enclosed capsule has a pentagonal outline and is closely pressed against the peri- 

 phragm save at the angles. The capsule wall is usually thin and smooth. 



The tabulation is often well shown from the orientation of the processes, which in 

 some specimens are almost restricted to the plate boundary zone in simulate complex- 

 es, whilst in others they are more numerous and irregularly arranged. The hollow, 

 simple or branched processes tend to be concentrated on the ambitus of the peri- 

 phragm. As in the typical W. Homomorpha, the processes show considerable 

 variation distally. They are nearly always closed with acuminate, blunt or bifid tips, 

 but several specimens with processes that open distally with aculeate or entire 



