. Bulletin of the British Museum (Natural History), Geology. MESOZOIC AND CAINOZOIC DINOFLAGELLATE CYSTS 163 processes. Such cingular processes are especially characteristic of the genus Siirculosphaeridiiim, and make specimen orientation comparatively easy. The form of the processes and the exact distribution of the non-cingular processes, although difficult to determine, indicate that this species does belong to this genus. Material (figured). () slide ¥.51736(1). Lower Oxfordian, Dorset, England. Upper Jurassic, England. Dimensions. Figured specimen : diameter of central body 37 by
. Bulletin of the British Museum (Natural History), Geology. MESOZOIC AND CAINOZOIC DINOFLAGELLATE CYSTS 163 processes. Such cingular processes are especially characteristic of the genus Siirculosphaeridiiim, and make specimen orientation comparatively easy. The form of the processes and the exact distribution of the non-cingular processes, although difficult to determine, indicate that this species does belong to this genus. Material (figured). () slide ¥.51736(1). Lower Oxfordian, Dorset, England. Upper Jurassic, England. Dimensions. Figured specimen : diameter of central body 37 by 47[x, length of processes up to 30[jl. Surculosphaeridium longifurcatum (Firtion) PI. 8, figs. 7, II, Text-figs. 43, 44 1952. Hystrichosphaeridiuni longifurcatum Firtion : 157, pi. 9, fig. i ; text-fig. i, H, K, L and M. 1963. Baltisphaeridiiim longifurcatum (Firtion) Downie & Sarjeant : 91, Description. A number of specimens have been found in the British Cenomanian which appear to be comparable to Firtion's species from the Cenomanian of France. The central body is subspherical. The periphragm is smooth and gives rise to a more or less constant 26 processes in a complete specimen. An angular archaeopyle is commonly present, the detached apical region bearing 4 apical processes. The processes are closed distally and are rather variable in form, being simple, lobate foliate or digitate. Some of the processes, particularly those marking the cingulum, are deeply branched. In the Upper Cenomanian particularly, the cingular processes, each reflecting a cingular plate, may be completely subdivided. Thus there appears to be two instead of one cingular process for each V" f. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original British Museum (Natural History). London : BM(NH)
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