1935 

 1937 

 1 941 

 1948 

 ?I952 



1952 

 1955 

 1959 

 1963 

 1963 



1963 

 1963 



MESOZOIC AND CAINOZOIC DINOFLAGELLATE CYSTS 49 



Achomosphaera ramulifera (Deflandre) 

 PL 2, fig. 3 



Hystrichosphaera cf. ramosa (Ehr.) ; Deflandre, pi. 5, fig. n. 



Hystrichosphaeridium ramuliferum Deflandre : 74, pi. 14, figs. 5, 6 ; pi. 17, fig. 10. 

 Hystrichosphaeridium ramuliferum Deflandre ; Conrad : 2, pi. 1, fig. J. 

 Hystrichosphaevidium ramuliferum Deflandre ; Pastiels : 39, pi. 3, figs. 17-19. 

 Hystrichosphaeridium ramuliferum Deflandre ; W. Wetzel : 398, pi. A, fig. 9 ; text- 

 fig- 9- 

 Hystrichosphaeridium ramuliferum Deflandre ; Deflandre, text-fig. 4. 

 Hystrichosphaeridium ramuliferum Deflandre ; Valensi : 594, pi. 4, fig. 6. 

 Hystrichosphaeridium ramuliferum Deflandre ; Gocht : 71, pi. 3, fig. 9. 

 Hystrichosphaeridium ramuliferum Deflandre ; Baltes : 586, pi. 7, figs. 13, 17, 18. 

 Hystrichosphaeridium ramuliferum Deflandre ; G6rka : 59, pi. 8, fig. 3 ; text-fig. 6, 



figs- 3. 4- 

 Baltisphaeridium ramuliferum (Deflandre) Downie & Sarjeant : 92. 

 Achomosphaera ramulifera (Deflandre) Evitt : 163. 



Description. Representatives of this species occur infrequently in the Ceno- 

 manian of England and are very similar to the type material. The central body is 

 smooth or very slightly reticulate and upon it may be traced lines marking the 

 reflected plate boundaries. The processes are hollow, often possessing rather 

 bulbous bases, and having usually trifurcate with bifurcating extremities. The 

 cingular processes are commonly joined and a distinctive apical process is usually 

 present. The London Clay forms attributed to A. ramulifera often differ from the 

 type material in having processes with more than three furcations, exceptionally 

 six spines arising from one process . When six spines are present , they have apparently 

 resulted from the elongation of the bifid tips of the three original furcations. Pastiels 

 (1948) also recorded forms from the Ypresian of Belgium which may have more than 

 three spines arising from a single process. The surface of the central body may be 

 smooth or slightly granular. 



The species has a stratigraphic range from the Cenomanian to the Middle Miocene. 



As with Hystrichosphaera ramosa, A. ramulifera is probably divisible into a number 

 of varieties ; one obvious variety would be those forms possessing multifurcate 

 processes as opposed to the trifurcate processes of the type material. In the present 

 state of knowledge, however, it is better to proceed cautiously in the erection of 

 varieties, since too few specimens have been studied for an adequate picture to have 

 emerged. 



Dimensions. Cenomanian forms : diameter of central body 40-56^, length of 

 processes up to 36(0.. Number of specimens measured, 4. London Clay forms : 

 diameter of central body 24-541;., length of processes up to 35fi.. Number of speci- 

 mens measured, 10. 



