MILIOLIDAE - Acta Palaeontologica Polonica

MILIOLIDAE FROM MIOCENE OF POLAND 125
Material. - About 100 specimens (ColI. No. F-176, Sec. No. 199, 200,
202-204).
Dimensions: L 0.75-0.9; B 0.55-0.85; T 0.48-0.5.
Description. - Test thick, broadly oval, oval in cross-section, periphery
broadly rounded; chambers broad, inflated, semicircular, middle chambers
very small, often invisible, two or three chambers visible from outside;
sutures flat, indistinct, with a narrow border along the chamber edges;
wall thin; surface smooth, polished; aperture large, circular, strongly
oblique, surrounded with a thickened rim, and with large tooth bifid at
the end and projecting above the aperture edge.
Variability. The test may be more or less inflated, being often triloculine
and nearly circular in cross-section in small specimens, whereas large
biloculine forms are laterally compressed and with sligthly depressed
sutures. The length of the apertural tooth is variable as well, being sometimes
short, and spine-shaped, or usually long and solid, projecting above
the aperture border, and with a specifically perforate septum.
lmm
Fig. 41. Morphological variability, internal structure and dimorphism of Sinuloculina
cyclostoma (Reuss), Upper Tortonian, WElglinek; 1,2 - biloculine forms, mega I (?)
generations, initial part irregularly triloculine, then planospiral; 3 - biloculine form,
micro generation, initial part cryptoquinqueloculine. then pseudotriloculine; 4 - tri;.
loculine form, mega I (?) generation, internal structure pseudotriloculine; a front
view, b apertural view, c cross-section. .