Helenea progonos
Set number: 3099
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10µm
Helenea progonos Varol, in prep.
From the Greek progonos, meaning “ancestor” or “forebear”, referring to its possible ancestral relationship to Helenea.
Length: 7.71 µm; width: 5.60 µm; width of the pelaga: 1.46 µm; width of the central area: 2.68 µm; ellipticity: 1.37.
Normally elliptical species (ellipticity: >1.3) of Helenea are characterised by an axial cross that may be slightly rotated relative to the axis of the placolith. The arms of the cross have pointed terminations and support a short distal process with a distinct square-shaped termination.
The entire species exhibits first-order, slightly greyish-white interference colours. The pelaga of Helenea progonos exhibits inclined extinction and length-fast (-) elongation in its natural settling position, as seen in plan view under crossed polars.
Helenea progonos is distinguished from Helenea acuminata by having a normally elliptical outline rather than a subcircular outline. Both species have a central cross with arms terminating in blunt points.