MILIOLIDAE - Acta Palaeontologica Polonica

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106 EWA l.UCZKOWSKA Dimorphism and ontogeny. The sections show forms of the micro generation, PD 10 fA. (Text-fig. 36/1) and mega I generation, PD 50-70 J.l (Text-fig 36/2-5). The internal structure of the micro generation is cryptoquinqueloculine initially, then pseudotriloculine, e.g. with one acute and two obtuse (over 130°) angles, measured between the three last chambers (Text-fig. 36/1). The mega I generation is cryptoquinqueloculine throughout. There also exist specimens with four (PI. XX, Fig. 1) or even five chambers visible from outside (PI. XX, Fig. 2). Remarks. - This species differs from Miliolinella valvulaTis (Reuss) in its more elongated test shape, thinner wall, and broader, transversely contracted aperture. Distribution. - Poland: Tortonian (Gliwice Stare, Grabki Duie, Karsy, Korytnica, Krywald, Ligota Zabrska, Zrecze). Bulgaria: Tortonian, the north-western and north-eastern regions of Bulgaria. Czechoslovakia: Lower Tortonian, Zidlochowice. Romania: Tortonian, Kostej in Banat. USSR: Lower Oligocene, West Siberia and Middle Asia; Middle Miocene, West-Precaucasian region, Dagestan, Georgia, Abkhasia, Crimea; Lower Tortonian, Volhyn-Podolia Platform. X Miliolinella valvularis (Reuss, 1851) (Pl. XX, Figs 4, 5; Text-fig. 37) 1851. Triloculina valvularis Reuss; A. E. Reuss, p. 85, Pl. 7, Fig. 56. Material. - About 100 specimens (ColI. No. F-159, Sec. No. 285, 288, 294-296). Dimensions: L 0.35-1.0; B 0.32-0.85; T 0.25-07. Description. - Test regularly oval, periphery broadly rounded, crosssection broadly oval or triangular-oval in outline; chambers broad, inflated, slightly narrowing at both ends, middle chamber convex, oval or narrowly oval with tapering ends, occupying one-third of the breadth of the front side; sutures somewhat depressed, with longitudinal groove along the chamber edges; surface smooth; wall thick; aperture semicircular or slightly triangular, with sinuous border and tongue-shaped flap, the central portion of which is slightly depressed. Variability. The number of chambers visible from outside is variable, three in typical specimens or two in non-typical ones in which the last chambers embrace those of the previous whorls so that only a narrow trace of the third chamber remains between them (PI. XX, Fig. 5a-c). The aperture flap of such "pseudobiloculine" specimens is thickened and convex, without a depression in the central part. The "pseudobiloculine" specimens resemble Pyrgoella, but they never have chambers arranged in a single plane. Dimorphism and ontogeny. The specimens sectioned represent the micro generation, PD 10 ~, and the mega I generation, PD 70-100 ~l. The
<strong>MILIOLIDAE</strong> FROM MIOCENE' OF POLAND 107 internal structure of both generations is initially triloculine, then irregularly triloculine, one of the angles measured between the three last chambers being less than 90 0 and two exceeding 120 0 (Text-fig. 37/2,3). Large two-chambered forms have always an irregular triloculine (pseudo lmm Fig. 37. Ontogeny and dimorphism of Miliolinella val'/;ularis (Reuss), Upper Tortonian, Krywald borehole, depth 72-74 m; 1-pseudobiloculine form, micro generation; 2 pseudotriloculine form, mega I generation; 3 - cryptoquinqueloculine form, mega I generation; a front view, b apertural view, c cross-section. triloculine) chamber arrangement despite their "pseudobiloculine" appearance (Text-fig. 37/1). Remarks. - Pseudobiloculine forms differ from Pyrgoella ventruosa (Reuss) and P. controversa (Bogdanowich) in having larger tests, thicker walls, a more oval shape and pseudotriloculine internal structure. They
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