MILIOLIDAE - Acta Palaeontologica Polonica

MILIOLIDAE FROM MIOCENE OF POLAND 39
oval, flattened, periphery broadly rounded; middle chamber small, narrow
and flat; sutures distinct, slightly depressed; wall thin; surface smooth,
covered with numerous regular fine longitudinal striae; aperture large,
oval, with flexuose margin, surrounded with a thickened rim.
Variability. No shape variation is observed. A distinctive feature of
the species is the presence of characteristic fine striae, which are hardly
visible in some specimens.
Dimorphism. Quinqueloculine forms belong mostly to the megalospheric
I generation with a proloculus 70~ in diameter, massiline forms
belong to the microspheric generation with a proloculus 20ll in diameter
(Text-fig. 6). No differentiation of generations is observed in the test
morphology.
lmm
Fig. 6. Dimorphism of Quinqueloculina alexandri sp. n., Lower Tortonian, Korytnica;
1-MS, micro generation, 2 - QS - mega I generation; a front view, b apertural
view, c cross-section.
Remarks. - The quinqueloculine stage differs from QuinqueZoculina
boueana d'Orbigny from Nussdorf (Austria) in having a more oval shape
and far more abundant fine striae. Specimens of Q. boueana from Voslau
(Austria) at the author's disposal have a slenderer shape and prominent
longitudinal striae, about 12 on each chamber. According to A. K. Bogdanowich,
who examined Q. alexandri, this species corresponds closely to
the forIns designated by him as Quinqueloculina aff. boueana. From