Paleocene, Late Oligocene and Post-Oligocene Silicoflagellates in Southwestern Pacific Sediments Cored on DSDP Leg 21

Silicoflagellate and Coccolith Stratigraphy, Southeastern Pacific Ocean, Deep Sea Drilling Project Leg 34

“…Plate: An equant sheet-like apical structure that may be smooth or granular and is typically triangular in taxa such as Corbisema geometrica, and square in taxa such as Dictyocha deflandrei, both of which have struts connecting the plate to the basal ring. In Vallacerta the plate covers the entire interring area and arches slightly (McPherson and Ling, 1973 Jerkovic (1969Jerkovic ( , 1971, Wornardt (1971), Dumitrica (1973a), and McPherson and Ling (1973). The electronmicrographs of Bachmann and Keck show areas with ridges where nodes are missing and areas where both are present on the same specimen.…”

“…The individual protuberances, or nodes, may terminate bluntly, in points, or in irregular shapes. Their spacing suggests that they may be enlargements of line intersections in reticulate surface texture (see illustrations of Wornardt, 1971;and Dumitrica, 1973a).…”

“…The two minor axis portals are distinctly smaller than the major axis portals. Although Dictyocha brevispina is still a mixed form-taxon involving numerous nomenclatural problems (see discussions of Dumitrica, 1973b), several distinctive members of the group, such as Dictyocha lingii Dumitrica, have been recently distinguished. Distinguishing paleoecologically or stratigraphically significant subgroups of D. brevispina is still possible, but an extreme range of intraspecific varition for this form, demonstrated by Deflandre (1950), will necessitate more thorough studies than are presently available.…”

“…Remarks: Dumitrica (1973b) pointed out that there is considerable confusion as to what is and what is not Dictyocha fibula. Loeblich et al (1968, pi.…”

“…(2) If the type is as discussed by Dumitrica (1973b), then specimens tabulated in this report as D. brevispina should be assigned to D. fibula; the D. stapedia group could remain as cited; but, the form tabulated here as D. fibula fibula, based on Ehrenberg (1854), would require a different name, perhaps as a subspecies within the D. perlaevis group.…”