Calculites kratiras
Set number: 2998
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10µm
Set number: 2999
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10µm
Calculites kratiras Varol, in prep.
From Greek kratiras, crater, referring its large hollow distal process
Subcircular species of Calculites are constructed of a narrow outer wall and four central crystalline blocks that support a very large, hollow distal process, subcircular to circular in cross-section. The process is supported by ten to twelve struts, which produce depressions between adjacent struts.
The sutures extending from the distal process curve gently towards the periphery between the crystalline blocks and form an obliquely oriented cross.
In plan view under crossed polars, the outer wall and the crystalline blocks display first-order yellow interference colours, whereas the distal process exhibits second-order brownish-blue interference colours.
Calculites kratiras exhibits parallel extinction (extinction angle 0°) and length-slow (+) elongation in its natural position.