MILIOLIDAE - Acta Palaeontologica Polonica

MILIOLIDAE FROM MIOCENE 'OF POLAND 99
.Distrib1;Ltion. - Poland: Tortonian (Gliwice Stare, Korytnica, Ligota
Zabrska, Niskowa, W~glinek, Wieliczka). Romania: Tortonian, Kostej in
BanaL USSR: Upper Tortonian, the Volhyn-Podolian Platform.
Genus Sigmoilopsis Finlay, 1947
The distinction between the quinqueloculine stage of Sigmoilopsis and
that of Siphonaperta Vella, 1957, is difficult in some cases, the more so as
within one species of Sigmoilopsis there occur specimens with broad
flattened tests and those of juvenile stage with thicker tests, resembling
Siphonaperta (e.g. in Sigmoilopsis arenaria (Brady) from the Indian
Ocean, or in S. foeda (Reuss), from the Miocene of Wieliczka. The juvenile
stage of Sigmoilopsis is generally characterized by its more compactly
coiled test and inconspicuous middle chambers, which can hardly be
distinguished while looked at from the outside.
X Sigmoilopsis foeda (Reuss, 1850)
(PI. xv, Figs la, b - 4a, b; Text-fig. 34/5-9)
1850. Quinqueloculina foeda Reuss; A. E. Reuss, p. 384, Pl. 50, Figs 5, 6.
1957. Sigmoilina plana Smigielska; T. Smigielska, p. 260, PI. 16, Fig. 5.
Material. - Over 500 specimens (ColI. No. F-152, Sec. No. 414, 420­
423).
Dimensions: L 0.85-1.5; B 0.5-1.0; T 0.25-0.3.
Description. - Test massive, thick, flat, oval or rhomboid in shape,
periphery broadly rounded; outer chambers tubular, arcuate, 2-3 middle
chambers indistinct; sutures indistinct; wall rough, irregularly covered
with sand grains of different size, protruding above the surface; aperture
circular, at the end of a short narrow neck, with a thickened rim and
a short tooth, widened at the end.
Variability and ontogeny. - The shape and thickness of the test are
various, which is predominantly connected with ontogeny. The quinqueloculine
stage is of relatively large size and this is why slender
inflated specimens (PI. XV, Fig. 3) occur beside the oval flattened specimens
of the mature stage (PI. XV, Figs 1, 2, 4). Sporadically the quinqueloculine
stage is so large than it is poorly distinguishable from
specimens belonging to Siphonaperta; it is usually marked by thicker walls,
non-prominent middle chambers and indistinct flattened sutures (Text-fig.
34/4,6). The sections show a distinct large quinqueloculine stage and
2-3 chambers of the planospiral stage (Text-fig. 3417-9). The specimens
sectioned belong to the micro generation; PD 20-60 f.l.
7*