The Ants of the Baltic Amber. 13 



'punctatiis of Europe, is represented by 494 specimens. Subtracting 

 this number also from the 4961 specimens, we have left only 1190 

 specimens to represent all the remaining species and genera. It will 

 be seen, therefore, that most of the species of truly extra-European 

 affinities were rare in the amber forests and that the most abundant 

 ants, apart from the two species of Iridomyrmex, belonged to Formica 

 and Lasius, which are even today the two dominant European genera^). 

 A pronounced tendency towards a supplanting of the Indiau, Malayan 

 and Australian elements in the mixed amber fauna by palearctic ele- 

 ments is therefore very apparent as far back as Lower Oligocene 

 times, although it seems to have been permanently accomplished only 

 by the advent of the Glacial Epoch. 



The foregoing considerations suggest several questions that are 

 not easily answered. Did all the amber species coexist as members 

 of a single fauna throughout the life-time of the amber forests or did 

 they belong to successive faunas, the Indomalayan and Australian 

 elements belonging to an earlier and warmer, the palearctic to a later 

 and cooler portion of the Lower Oligocene? Or were the differences 

 of altitude or latitude or of both in the amber forests sufficient to 

 produce two different faunas which coexisted though occupying diffe- 

 rent stations? Answers to these questions can come only from a more 

 precise knowledge of the conditions under which the amber was formed 

 and preserved. That the amber forests were rather extensive is clear 

 from Tornquist's statement-) that their southern boundary extended 

 across what is now central Sweden eastward through Finland and 

 Estland and up the Dvina River to Minsk and Tobolsk in Western 

 Russia, while the adjacent sea covered not only wha: is now northern 

 Germany but also the region drained by the Vistula, Niemen and 

 Dnieper Rivers as far as the Black Sea, That the climate of the 

 umber country was subtropical is evident from its vegetation. Some 

 of the earlier paleontologists, like Heer, were convinced that the country 

 was not flat, but mountainous, and that the masses of hardened amber 

 were detached from the trees and witli other vegetable detritus carried 

 down by torrents to the region in which they are now found, namely 

 the bed of the Baltic Sea and the soil of northern Germany which 

 it once covered. 



1) Prenolepis is still a dominant genus in North Anterica and tropical .Apia bnt 

 has ceased to occupy this ])Osition in Europe. 



2) Geologie von Ostpreufien, 1910. 



