62 MESOZOIC AND CAINOZOIC DINOFLAGELLATE CYSTS 



Emended diagnosis. Central body spherical to ovoidal with characteristic 

 reflected tabulation of 4', 6", 6c, 5'", ip, 1"" with variable number of sulcal processes. 

 Processes well developed, tubiform, with sub-quadrate distal openings. Distal 

 margins entire or denticulate. Number of processess present 25 to 30. Apical 

 tetratabular archaeopyle practically always present. 



Holotype. Slide AJ56, Laboratoire de Micropaleontologie, Ecole Pratique des 

 Hautes Etudes, Paris. Senonian ; France. 



Material (Figured). B.M.(N.H.) slide ¥.51734(1). 146 feet above base of 

 London Clay ; Whitecliff Bay, Isle of Wight. 



Dimensions. Range of specimens from type material (Deflandre 1937) ; dia- 

 meter of central body 35 to 40[x, length of processes 25 to 30[x, the number of processes 

 is approximately 30. Range of London Clay specimens : diameter of central body 

 30-44^, length of processes 14-20^. Number of specimens measured, 4. 



Description. The surface of the central body may be smooth or slightly granular, 

 and composed of two layers, the endophragm and periphragm (absent beneath the 

 processes). The processes expand gradually towards the distal sub-quadrate 

 opening, which is up to i8[i across in the London Clay forms. Medially the processes 

 rarely exceed iOfj. and are usually much less. The wall of the processes (composed 

 of periphragm) is slightly fibrous. The distal margin can be serrate, undulose or 

 even aculeate. Processes may be perforate distally. 



Remarks. The London Clay specimens have rather short and broader processes 

 than the holotype and are perhaps a variety of H. salpingophorum. The ribs, 

 illustrated by Element (i960), extending along the length of the processes and run- 

 ning into the central body have not been observed. The specimen figured by 

 Lejeune-Carpentier (1940, text-fig. 8) is very similar to the London Clay forms. 



H. salpingophorum (London Clay) is generally easily distinguished from H. tubi- 

 ferum. However certain specimens from the London Clay are transitional, often 

 showing the circle formed at the junction of the processes and the endophragm. A 

 close relationship with H. tubiferum is also indicated by the identical tabulation and 

 intratabular processes. 



The Jurassic forms formerly attributed to H. salpingophorum are transferred 

 below to Hystrichosphaeridium costatum sp. nov. 



Hystrichosphaeridium costatum sp. nov. 

 PI. 10, fig. 4 



?i938. Hystrichophaeridium salpingophorum (Deflandre) ; Deflandre : 186, pi. 10, figs. 1-3. 



?i947. Hystrichosphaeridium salpingophorum (Deflandre) ; Deflandre, text-fig. 1, no. 6. 



?i952. Hystrichosphaeridium salpingophorum (Deflandre) ; Deflandre, text-fig. 10. 



i960. Hystrichosphaeridium salpingophorum (Deflandre) ; Klement : 55, pi. 7, figs. 3-5 ; 

 text-fig. 31. 



i960. Hystrichosphaeridium salpingophorum (Deflandre) ; Sarjeant : pi. 13, fig. 7. 



1961. Hystrichosphaeridium salpingophorum (Deflandre) ; Sarjeant : 99, pi. 15, fig. 7. 



