Calculites koilos
SEM photo of Calculites koilos from Hatter & Wise, 1980 (Pl. 28, Fig. 2)
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Calculites koilos Varol, in prep.
From the Greek koilos, meaning “hollow”, referring to the hollow distal process.
Elliptical species of Calculites are constructed of a narrow outer wall and four central crystalline blocks that support a large, hollow distal process, elliptical in cross-section and aligned diagonally. The process is supported by six to nine struts, which produce depressions between adjacent struts. The scanning electron microscope image illustrated in Plate 28, Figure 2, of Hattner & Wise (1980) provides the best example of this detailed structure.
The sutures extending from the corners of the distal process are curved towards the periphery between the crystalline blocks and form a cross that is rotated slightly relative to the long axis of the ellipse.
In plan view under crossed polars, the outer wall and the crystalline blocks display first-order greyish-white interference colours, whereas the distal process exhibits whitish-yellow interference colours.
Calculites koilos exhibits symmetrıcal extinction (extinction angle 45°).
Hattner, J. G. & Wise, S. W. 1980. Upper Cretaceous calcareous nannofossil biostratigraphy of South Carolina. South Carolina Geology 24: 41-117.