MILIOLIDAE - Acta Palaeontologica Polonica

MILIOLIDAE FROM MIOCENE OF POLAND 47
and therefore a large amount of material must often be examined to find
a single specimen. On the other hand, the quinqueloculine forms are
abundant and include all the three generations, which can be distinguished
however only in cross-sections. PD: micro - 20-25/-l' mega 1- 130-150/-l'
mega II - 250/-l.
Ontogeny. - An examination of cross-sections shows that the quinqueloculine
stage of massiline forms of micro generation is composed of
about 16-18 chambers, which gradually but considerably increase in size
lmm
3.@cQ)
~~~"
&~o
3c 4c 5c
Fig. 13. Ontogeny of QuinqueZocuZina buchiana d'Orbigny, Lower Tortonian, Korytnica;
1-QS, mega II generation; 2-5 - QS, mega I generation; a front view, b apertural
view, c cross-section.
and are followed by 2-3 massiline chambers in planes about 180 0
apart
(Text-fig. 12/1, 2), slightly sigmoiline in appearance. This is also seen in
cross-sections of intermediate forms to the massiline stage (Text-fig. 12/3).
The quinqueloculine forms of the mega II generation having a large proloculus
(Text-fig. 13/1) and those of the mega I generation having a smaller
proloculus (Text-fig. 13/2, 5) are composed of 7-10 chambers, gradually
increasing in size. The size of tests is rather connected with the size of
the proloculus than with the number of chambers, and the following
interdependence may be stated: large proloculus - small number of chambers
-large diameter of test; small proloculus - great number of chambers
- small diameter of test; minute proloculus - very great number
of chambers - large diameter of test.