MILIOLIDAE - Acta Palaeontologica Polonica

MILIOLIDAE FROM MIOCENE OF POLAND 119
Description. - Test nearly spherical, tapering at the top and truncate
at the base; chambers strongly inflated with the periphery rounded in the
upper part and becoming gradually acute towards the base; chamber sides
narrow at the top and broad at the base, having a peculiar sinuous threelobed
form; sutures indistinct; surface smooth, polished; aperture large,
circular, in nearly horizontal position, surrounded with a thickened rim,
and with a short bifid tooth.
Variability and ontogeny. The chamber periphery may be more or
less rounded, sometimes remaining rounded also at the base. The aperture
border is variable as well; it is usually in the shape of a thickened rim
protruding to the outside or a collar inclined to the inside. The specimen
sectioned belongs to the mega I? generation; PD 120 f.l. The internal
structure is biloculine throughout (Text-fig. 39/8). The juvenile specimens
are more elongated than the adult ones.
Remarks. - Our specimens have more acute periphery and the threelobed
form of the lower part, in comparison with d'Orbigny's illustration.
However, as among the members of this species there are also some
specimens with the poorly developed acuteness of the periphery, it may
be assumed that the rounded periphery lies within the limits of intraspecific
variability.
Distribution. - Poland: Upper Tortonian (Gliwice Stare, Wf;glinek).
Recent: Cuba and Jamaica.
+ X Pyrgo truncata (Reuss, 1867)
(PI. XXII, Fig. la, b; Text-fig. 39/1)
1867. Biloculina bulloides d'Orbigny var. truncata Reuss; A. E. Reuss, p. 53, PI. 2,
Fig. l.
1868. Biloculina anodonta Karrer; F. Karrer, p. 133, PI. 1, Fig. 6.
1868. Biloculina bulloides d'Orbigny var. calostoma Karrer; ibidem, p. 132, PI. 1,
Fig. 4.
Material. - About 300 specimens (ColI. No. F-l73, Sec. No. 408, 409).
Dimensions: L 0.45-1.8; B 0.4-1.8; T 0.4-1.7.
Description. - Test circular, sometimes somewhat tapering at the top,
broadly oval in cross-section; chambers strongly inflated, the penultimate
chamber of nearly the same size as the last one, being narrower and
truncate at the base; periphery rounded, chamber sides sloping and forming
a narrow border around the penultimate chamber; sutures depressed;
surface smooth, polished; aperture semicircular, sometimes slightly protruded
and truncate, with a low and broad tooth and lateral processes.
Variability and ontogeny. - The test shape var!es from slightly
elongated, with the penultimate chamber extended downwards and truncate,
to circular, nearly spherical, with the penultimate chamber circular
too. Large, circular forms may lack the tooth, as in Pyrgo anodonta (Kar-