. Bulletin of the British Museum (Natural History), Geology. MESOZOIC AND CAINOZOIC DINOFLAGELLATE CYSTS 1^5 Gonyaulacysta cassidata (Eisenack & Cookson) PI. 14, figs. 3, 4 ; Text-fig. 31 i960. Gonyaulax helicoidea subsp. cassidata Eisenack & Cookson : 3, pi. i, figs. 5, 6. 1962. Gonyaulax cassidata Eisenack & Cookson ; Cookson & Eisenack : 486, pi. 2, figs, i, 2. 1964. Gonyaulax cassidata Eisenack & Cookson ; Cookson & Hughes : 42, pi. 5, fig. 10 only. Emended diagnosis. A Gonyaulacysta with thin-walled, broadly ovoidal theca, surmounted by apical pericoel terminating
. Bulletin of the British Museum (Natural History), Geology. MESOZOIC AND CAINOZOIC DINOFLAGELLATE CYSTS 1^5 Gonyaulacysta cassidata (Eisenack & Cookson) PI. 14, figs. 3, 4 ; Text-fig. 31 i960. Gonyaulax helicoidea subsp. cassidata Eisenack & Cookson : 3, pi. i, figs. 5, 6. 1962. Gonyaulax cassidata Eisenack & Cookson ; Cookson & Eisenack : 486, pi. 2, figs, i, 2. 1964. Gonyaulax cassidata Eisenack & Cookson ; Cookson & Hughes : 42, pi. 5, fig. 10 only. Emended diagnosis. A Gonyaulacysta with thin-walled, broadly ovoidal theca, surmounted by apical pericoel terminating in short horn. Tabulation 4', la, 6", 6c, 6'", ip, i"" ; plate boundaries demarcated by high, delicate crests with smooth or denticulate edges. Cingulum strongly spiral, of moderate breadth : sulcus broaden- ing posteriorly, weakly sigmoidal. (A median dorso-ventral plane would barely intersect the two ends of the cingulum.) Surface of shell smooth or only minutely granular : irregular scatter of tubercles present in some specimens. HOLOTYPE. Specimen , National Museum of Victoria, Australia. Lower Cretaceous (Albian) ; Santos's Oodnadatta bore, South Australia, at 327 feet depth. Material (figured). Geol. Surv. Colin, slide (i). Chalk, Geological Survey Borehole, Fetcham Mill, Surrey, at 730 feet depth. Upper Cretaceous (Cenomanian).. 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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