. Bulletin of the British Museum (Natural History), Geology. . A B Fig. 19. Thalassiphora pelagica (Eisenack) Eisenack & Gocht i960. Reflected tabulation of dorsal surface. A. Interpretation from Gocht (1968 : pi. 27, fig. 3a ; 1969 : text-fig. 47). B. Interpretation based on reflected tabulation of Thalassiphora delicata Williams & Downie 1966c emend. The precingular archaeopyle (3") is represented by shading. can be interpreted in terms of the reflected tabulation of T. delicata (Fig. 19). On this basis, the forms described by Gocht as initial and intermediate stages in the deve
. Bulletin of the British Museum (Natural History), Geology. . A B Fig. 19. Thalassiphora pelagica (Eisenack) Eisenack & Gocht i960. Reflected tabulation of dorsal surface. A. Interpretation from Gocht (1968 : pi. 27, fig. 3a ; 1969 : text-fig. 47). B. Interpretation based on reflected tabulation of Thalassiphora delicata Williams & Downie 1966c emend. The precingular archaeopyle (3") is represented by shading. can be interpreted in terms of the reflected tabulation of T. delicata (Fig. 19). On this basis, the forms described by Gocht as initial and intermediate stages in the development of T. pelagica should be excluded from this species, and I agree with Drugg (1970 : 819) that some of these forms should be included in Muratodinium Drugg 1970. If the concept of Thalassiphora is restricted to the original definition by Eisenack & Gocht (i960), together with the possible definition of plate areas, then the species assigned to Thalassiphora, T. pelagica, T. delicata and T. reticulata Morgenroth 1966b, exhibit a considerable range of texture and structure of the periphragm and endophragm. In this respect T. pelagica appears to be more closely related to forms such as Muratodinium and Adnatosphaeridium ? patulum Williams & Downie 1966c than to T. delicata, but in terms of the present accepted treatment of fossil dinoflagellate cyst taxa this relationship would be at supra-generic level. Thalassiphora pelagica (Eisenack) Eisenack & Gocht i960 Fig. 19 ; PI. 16, figs 4-5 1938 Bion pelagicum Eisenack : 187 (nom. nud.). 1954 Pterospermopsis pelagica Eisenack : 71 ; pi. 12, figs 17-18. i960 Thalassiphora pelagica (Eisenack) Eisenack & Gocht: 513 ; text-figs 1-3. Dimensions. Observed range : periphragm 108 x 126 /x to 212 x 176 /x ; endo- phragm 60 x 66 fL to 98 x 94 ju, ; length of keel up to 20 /la. (n = 9). Remarks. Specimens here assigned to T. pelagica are dorsoventrally flattened and have a relatively thick-walled central body. The peri
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