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Cyclonephelium membraniphorum
Cyclonephelium "membraniphora" (Cookson and Eisenack, 1962b, p.495, pl.6, figs.8-14) Below, 1981a, p.22. Holotype: Cookson and Eisenack, 1962b, pl.6, fig.9. NOW Cauveridinium. Originally Cyclonephelium, subsequently Maghrebinia, thirdly (and now) Cauveridinium. Age: Albian-Cenomanian.
Original description: Cookson and Eisenack, 1962, p.495
Shell apparently concavo-convex, circular to subcircular in outline. Circumferential border zone delimited by two thin membranes of equal width, each of which is supported by rather widely spaced, equidistant, radial fibres. These fibres arise from the peripheral surfaces of the shell, and their bases are connected with another tangentially. They are simple or capitate and relatively stout. Sometimes fine radial striae cross the width of the membranes, in which cases the edge appear to be finely toothed. Occasionally a union between opposing fibres may occur, with the formation of wide funnel-like structures. The sculpture of the shell varies from very finely to coarsly granular.
Supplemental description: Davey, 1969, p.167
The shell is always dorso-ventrally flattened, both the apex and antapex being circular to subcircular in outline. An apical archaeopyle is always developed, with a zigzag margin and sulcal notch. The bald areas, tvpical of this genus, may be relatively large or quite small and are surrounded by high membranes.
The latter are braced by stout supports which arise from lines of thickening on the shell surface. These lines of thickened periphragm may be curved and may form semi-circular rings. When the latter are present, the membranes are in the form of wide tubular projections. The periphragm of the shell wall and the membranes is granular or pitted. The membranes may sometimes be fenestrate.
In some specimens attributed to C. membraniphorum the bald areas are practically non-existent. The membranes in these forms are particularly well developed and commonly are in the form of wide tubes or funnels. Distally they have a subcircular to polygonal outline and may possess a thickened outer rim bearing irregular pieces of periphragm.
Original description: Cookson and Eisenack, 1962, p.495
Shell apparently concavo-convex, circular to subcircular in outline. Circumferential border zone delimited by two thin membranes of equal width, each of which is supported by rather widely spaced, equidistant, radial fibres. These fibres arise from the peripheral surfaces of the shell, and their bases are connected with another tangentially. They are simple or capitate and relatively stout. Sometimes fine radial striae cross the width of the membranes, in which cases the edge appear to be finely toothed. Occasionally a union between opposing fibres may occur, with the formation of wide funnel-like structures. The sculpture of the shell varies from very finely to coarsly granular.
Supplemental description: Davey, 1969, p.167
The shell is always dorso-ventrally flattened, both the apex and antapex being circular to subcircular in outline. An apical archaeopyle is always developed, with a zigzag margin and sulcal notch. The bald areas, tvpical of this genus, may be relatively large or quite small and are surrounded by high membranes.
The latter are braced by stout supports which arise from lines of thickening on the shell surface. These lines of thickened periphragm may be curved and may form semi-circular rings. When the latter are present, the membranes are in the form of wide tubular projections. The periphragm of the shell wall and the membranes is granular or pitted. The membranes may sometimes be fenestrate.
In some specimens attributed to C. membraniphorum the bald areas are practically non-existent. The membranes in these forms are particularly well developed and commonly are in the form of wide tubes or funnels. Distally they have a subcircular to polygonal outline and may possess a thickened outer rim bearing irregular pieces of periphragm.