. Bulletin of the British Museum (Natural History) Geology Supplement. i6j MESOZOIC AND CAINOZOIC DINOFLAGELLATE CYSTS Remarks. The diagnosis of this species has been emended to draw attention to the closed processes, which reflect a definite tabulation characteristic of the genus and the presence of an archaeopyle. The processes were originally considered to be open distally ; however, full re-examination of the holotype at high magnifications has not confirmed this. Surculosphaeridium vestitum (Deflandre) PI. 9, fig. 8 ; Text-fig. 42 1938 1938 1947 1952 1955 1960c Hystrichosphaeridium vestit
. Bulletin of the British Museum (Natural History) Geology Supplement. i6j MESOZOIC AND CAINOZOIC DINOFLAGELLATE CYSTS Remarks. The diagnosis of this species has been emended to draw attention to the closed processes, which reflect a definite tabulation characteristic of the genus and the presence of an archaeopyle. The processes were originally considered to be open distally ; however, full re-examination of the holotype at high magnifications has not confirmed this. Surculosphaeridium vestitum (Deflandre) PI. 9, fig. 8 ; Text-fig. 42 1938 1938 1947 1952 1955 1960c Hystrichosphaeridium vestitum Deflandre Hystrichosphaeridium vestitum Deflandre Hystrichosphaeridium vestitum Deflandre Hystrichosphaeridium vestitum Deflandre Hystrichosphaeridium vestitum Deflandre 189, pi. 11, figs. 4-6. Deflandre : 688, text-fig. 3. Deflandre, text-fig. 1, no. 3. Deflandre, text-fig. 7. Valensi : 587, pi. 2, fig. 8. Baltisphaeridium vestitum (Deflandre) Sarjeant : 397, pi. 13, fig. 8, pi. 14, figs. 13, 14. 1962a. Baltisphaeridium vestitum (Deflandre) : Sarjeant, pi. 12, figs. 3, 5, 6. Remarks. The holotype, from the Oxfordian of France, has been restudied by two of the authors ( and ), through the courtesy of Prof. Deflandre ; and the specimens figured by Sarjeant (1962a) from the Oxfordian of England have also been re-examined in the light of recent studies. The processes of this species are extremely variable in form, so making the elucidation of the reflected tabulation very difficult. The processes are intratabular, the larger ones reflecting one plate of the original dinoflagellate theca, while some of the finer ones, in contrast, occur in twos and threes and represent a larger process which has been subdivided down to the surface of the central body. Thus two or three of these processes may reflect a single plate. The most distinctive and characteristic processes are the ones lying in the cingular zone. These are either deeply furcate or completely divided into tw
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