Coptolithus diplax
Set number: 3220
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10µm
Set number: 3219
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10µm
Set number: 3218
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10µm
Craticiplacolithus diplax Varol, in prep.
From Greek di-, two, and plax, plate; referring to the two plate-like structures occupying the central area.
Elliptical placoliths composed of single-tiered distal and proximal shields and a narrow double-tube cycle. The narrow central area is completely covered by two plates.
Under cross-polarised light in plan view, the shields exhibit first-order white interference colours, while the tube cycles display first-order greyish-white interference colours. Both structures are characterised by inclined extinction lines and length-fast (–) elongation. Extinction angles of approximately 77° are observed on the distal side in both the shields and the tube cycles. The locking cycle remains in constant extinction, producing a dim cycle between the tube cycle and the shield. The central plates exhibit first-order whitish-grey interference colours.