Aktasia exarthromenos
Set number: 2784
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10µm
Aktasia exarthromenos Varol, in prep.
Small species of Aktasia (< 6.0 µm) have an axial cross with a dislocated, longer arm.
From Greek exarthromenos, meaning ‘dislocated’, referring to the displaced arm of the axial cross.
Maximum length: 4.3µm, Maximum width: 3.0µm
Small species of Aktasia (< 6.0 µm) have a zeugoid outer wall and a protolith inner wall composed of eight large sub-quadrilateral segments. The central area is completely covered by a single-row axial cross whose longer arm is dislocated along the shorter arm and lacks a distal process.
In plan view under XPL, the inner wall and axial cross display a white interference color, whereas the zeugoid outer wall is in constant extinction, indicating that the optical axis (c-axis) is perpendicular to the microscope stage.