Retecapsa rotunda
Set number: 3135
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10µm
Retecapsa rotunda Varol, in prep.
From the Latin rotunda, meaning “rounded” or “circular in outline”, referring to the outline of the placolith.
Circular species of Retecapsa are constructed of a cretarhabdid pelaga surrounding a large central area spanned by an indistinct axial cross that supports a distal process. The inter-cross area is occupied by lateral bars that delimit pores arranged in a single complete concentric cycle. Each quadrant typically contains four pores formed by three lateral bars, a feature characteristic of Retecapsa rotunda.
Retecapsa rotunda exhibits first-order, slightly greyish-white interference colours. In plan view under crossed polars, the pelaga shows inclined extinction, but its elongation direction cannot be determined with confidence.