98 
Dr. J. ÉHIK 
the circumstance that Prof. Méhely distinguished there a preglacial, a 
I.-st and a IL-nd interglacial period. 1 
The formation of the boreal or tundra fauna must have taken 
place already in the Pliocene of the arctic regions. The lemming for 
instance, — a most typical and still living representative of the tundras, — 
is well known from the lower Pleistocene strata of Northern Germany, 
so that its Pliocene occurrence must be taken for granted. This con¬ 
viction of mine is also born out by the geological profile accompanying 
the text. (The territory from which the boreal fauna originated is marked 
by 2a). And now let us see how the migration of this boreal fauna 
took place in consequence of the ice moving southwards and what kind 
of paleontological documents has it left back. (See the faunistical enume¬ 
rations enjoined and the geological profile of the Thiede-beds. Fig. 7.) 
The ice extending southwards drove also the animals in a southern 
direction. It is natural that larger boreal animals, able to wander over 
a good deal of ground, were the first in reaching the southernmost 
localities, beeing then followed by the smaller mammals, rather attached 
to the soil, whilst in the immediate vicinity of the ice again larger sized 
animals will be found. Thus the boreal fauna consisted of three different 
zones, that situated in the middle differing from the two lateral ones by 
containing smaller boreal forms, unfit to support extreme changes of 
climate and consequently inhabiting the middle zone, characterised by 
rather constant climatic conditions. — On spots indeed where a conti¬ 
nuous stratification took place and on which the respective pétrifications 
were conserved up to this day, this triple facies will really occur, 2 as 
proved by the Sirgenstein- and Thiede-strata. 
The result of the proceeding ice leaching and covering the earlier 
habitat of the faunae in question, was that the normal course of strati¬ 
fication stopped there, and even fossils belonging to this period are 
absent, the regions covered by inland-ice preventing the formation of any 
settlement. And the same thing can be stated in general, with respect 
to each successive phase on each spot, reached by the ice, until it attained 
the limits of its furthernmost expansion. In the vicinity of these limits 
one ought to be able to discern, besides the temporal also the spatial 
différenciation of the three mentioned subboreal faunistical zones. But 
the oscillations in the limits of the huge glaciers and special local cir¬ 
cumstances render a due appreciation of such a problem more difficult 
1 L. Méhely, Fibrinae Hungáriáé. Budapest 1914. 
2 Such beds are unfortunately very rare. See with respect to this question 
the quoted passage of Nehring, p. 90. footnote 1. 
