A new contribution to the knowledge of the Lower 
Tertiary Mollusca of the Aral Sea.* 
By Milan T. Lukovitch, (Beograd). 
The present paper embodies the result of the study of about 
three thousand specimens of the Lower Tertiary Mollusca collected 
in 1886 by Mr. W. Bateson between the Aral Sea and Lake Chalkar. 
The study of this collection was exceptionally interesting for the 
following reasons. 
1. Only very small collections have been examined before, al- 
though the beds that contain those fossils are the only Lower Ter- 
tiary Beds yet known in W. Siberia and Turkestan, rich in fossils. 
2. The age of the fauna has not been settled yet, since previous 
writers differ very much in opinion, giving to it different ages, be- 
ginnig with the Lower Eoeene and ending with the Lower Oligocene. 
3. Tis fauna together with the faunas of the same age from 
South Russia, seem to represent the original fauna from which has. 
gradually developed the Lower Oligocene Molluscan fauna of South 
Russia, and, at least in part, that of North Germany. Since it is be- 
lieved that a migration of the Molluscan fauna from the east to the 
west, towards the „Geosynclinal posthume“ must have taken place, 
an additional knowledge of the fauna of the East is of special interest. 
4. With the age of this fauna settled, some light will be thrown 
on two very interesting questions, viz.-(a) on the existenze of a Lo- 
wer Oligocene Transgression in these regions and(b) on the possi- 
bility of migration of the Siberian Artiodactyls into Europe, by the 
beginning of the Lutetian and Ludian; ie., whether the way by this 
time was open or not. 
As regards the age of the fauna, the most widely accepted 
opinion is that it is of the Lower Oligocene age, while the most 
recently expressed opinion is that it is ether a „Transition Eocene- 
Oligocene fauna“ or that there must exist both the Eocene and Lo- 
wer Oligocene beds in the complex, and that in those collections 
wich were examined, fossils were unitet. 
After a careful study of the fauna I have come to the conclu- 
sion, that it must have developed under conditions quite different 
from those in West Europe, and that these conditions have affected 
the persistence or changes of different species in a different way 
than in W. Europe. The fauna is apparently of the Eocene age, but 
it is difficult to define precisely its correlation with the European 
faunas. | believe that the beds containing this fauna were deposited 
during the Auversian and Bartonian period, without any interruption 
in sedimentation. If this fauna is Eocene, then it is highly improbabi« 
that an Oligocene transgression took place in this region; and if it 
is of the Auversian and Bartonian age, it renders possible the mi- 
gration of Artiodactyls irom Siberia during the Lutetian and Ludian, 
as will be shown in the followin pages. 
*) The palaeontological part of this paper will be published separately. 
