165 
consists not so much in the occurrence of the same species as in 
their general character. Yet about ten out of sixteen species quoted 
by Haug!) Fron v. Koenen work as most characteristic and common 
in the Budzak Series are also present in the Aral Sea Tertiary. Also 
if we eliminate the southern elements from the fauna of the Kiea 
Series (Kalinovka), the majority of the species are the same in both 
places. But the most important fact is that in the faunas of bot, 
the Budzak and the Kiev Series, some Oligocene forms are 
represented, the majority of which are also present in the Aral Sea 
Tertiary. It is also interesting that in the Budzak Series the number 
of the Oligocene species is smaller than in the Kiev Series in about 
.the same proportion as we have observed in comparing the faunas 
of the two horizons. It is worth mentioning also at this point that 
n many places in South Russia a complete continuity in sedimen- 
ation of the two series has been observed. From this account it is 
evident that the resemblance between the South Russian and Aral 
Sea beds and their faunas is not a slight one, and I am of the opi- 
nion that they are of the same age, the two horizons roughly cor- 
responding to the Budzak ad Kiev Series. 
Points of difference between the two faunas viz: fairly large 
percentage of different species and a somewhat larger number of 
Oligocene species in the Aral Sea Tertiary fauna can be explained 
not only by the great distance between them, but also by quite 
different conditions. For while the Sout Russian Basin communicated 
with the Mediterranean Sea, the Aral Sea was apparently in commu- 
nication with the Arctic Ocean. 
Von Koenen?) considers Budzak fauna as being of the Lutetian 
age, while K. Mayer Eymar*) who possessed the largest collection of 
specimens ever obtained from this Series, regards it as Bartonian (his 
Bartonian includes Auversian). N. Sokolov*) more recently agreed 
with this opinion, altbough he formerly accepted that of v. Koenen 
Owing to the relatively large percentage of the Lower Oligocene 
forms in the fauna of the Kiev Series, both of Mollusca and Fora- 
minifera. N. Sokolov?) is doubtful whether it is of the Upper Eo- 
cene or Lower Oligocene age. But other writers (Fuchs, v. Koenen, > 
Oppenheim,") Haug‘) etc.) are of the opinion that this fauna is in- 
contestably Eocene, only they do not say how it exactly stands in 
correlation with West and South-West European faunas of the Upper 
Eocene. The last expression of opinion concerning this fauna is in 
Haug’s Traite. He says, „The chracte of these faunas does not allow 
us to determine precisely the age whether Auversian or Pria- 
bonian, of the Kiew Series“. It still remains therefore to discuss 
both the lowest and the uppermost limit of the complex in the two pla- 
ces. The lowest limit can be taken as more or less settled by K. Mayer 
Eymar, since he has seen the largest number of specimens from the 
!) Traite de Geologie p. 1493. 
:) Kiev, Budzak and Traktemirov 1. c. p. 507—8. 
%) Verhandlungen d. Schweiz. naturf. Gesellschaft 1857 S. 19. 
*) Guide des excursions etc. 1. c. 
5) Guide des excursions etc. 1. c. p. 10. 
*) Priabonaschichten, Introduction. 
*) Traite p. 1493. 

