. Bulletin of the British Museum (Natural History), Geology. 274 DINOFLAGELLATE CYSTS AND ACRITARCHS This new species of Leptodinium compares with the species of the genus Psaligony- aulax and Tubotuberella, since it has a pronounced antapical pericoel. In the lack of apical horn and in the detail of the tabulation, it differs from Psaligonyaulax. Because Vozzhennikova was unable to give the tabulation of the genus Tubotuberella, it is impossible to be certain regarding the generic assignation for this new species. Leptodinium cf. subtile (Element) (PI. ii, figs, i, 2 ; Text-fig. 19) Descripti
. Bulletin of the British Museum (Natural History), Geology. 274 DINOFLAGELLATE CYSTS AND ACRITARCHS This new species of Leptodinium compares with the species of the genus Psaligony- aulax and Tubotuberella, since it has a pronounced antapical pericoel. In the lack of apical horn and in the detail of the tabulation, it differs from Psaligonyaulax. Because Vozzhennikova was unable to give the tabulation of the genus Tubotuberella, it is impossible to be certain regarding the generic assignation for this new species. Leptodinium cf. subtile (Element) (PI. ii, figs, i, 2 ; Text-fig. 19) Description. This form has a subspherical shell, without apical horn or pro- cesses. The cingulum is nearly circular, dividing the theca into two slightly unequal parts, the hypotract being larger than the epitract. Tabulation : 4', ia, 6", 6c, 5" ', 2p and 1" ". Apical plate 1' is long and situated in the anterior extension of the sulcus ; the three other apical plates are small. Intercalary plate ia is placed between plates 4' and 6", the latter plate is reduced to accommodate it. The other precingular plates are large. Three of the postcingular plates (2" ', 3" ' and 4" ') are large ; plates 1" ' and 5" ' are small because of the intercalary plates ip and 2p : ip placed below the first post- cingular plate, 2p placed below the fifth postcingular plate. Both of the intercalary plates are rather large. The single antapical plate 1" " is slightly polygonal and convex. The sutures between the plates, have high, membraneous crests, distal edge of the. Fig. 19. Leptodinium cf. subtile (Klement). Tabulation and the archaeopyle formation (plate 3" is missing). Left, ventral view ; right, dorsal view. xc. 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
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