76 The Loess of the Rhine and the Danube . [January, 
the southern mammals came northward in summer and re- 
treated to the south in winter. This explanation of the 
mingling of the remains of northern and southern mammals 
in the same deposit was first given by Sir Charles Lyell, 
and has been since advocated with great ability by Mr. 
Boyd Dawkins. That this is correct — and not that we 
have here the mixture of the remains of animals be- 
longing to two periods, one warm and the other cold, as 
urged by Mr. James Geikie — is evidenced by the land and 
fresh-water shells that accompany the remains of the Mam- 
malia. These could not, like the southern mammals, retreat 
to the south on the approach of winter, and they are all of 
a northern character, fitted to withstand great cold. Dr. 
Sandberger informs us that many of them still live in the 
higher parts of the Main valley above Bamberg. Others, 
such as Valvata naticina and Hyalina viridula , are only now 
found in the north and north-east of Europe. Pupa colu- 
mella is still living in the north of Russia, in Lapland, and 
on the Gemmi. Patula solaria is now found on the Eastern 
Alps and the Silesian hills, and others attain their southern 
limits at Frankfort.* From a consideration of these fadts 
Dr. Sandberger comes to the conclusion that the climate 
must have been much colder than at present. It would 
appear to have been so if we take the evidence of the shells 
only, but when we add that of the mixture of the remains 
of northern and southern mammals we are rather led to the 
opinion held by Sir Charles Lyell and Mr. Boyd Dawkins, fi 
that the winters were colder and the summers perhaps 
warmer than now ; that, in fadt, the climate was more con- 
tinental, in consequence of the western coast of Europe 
having then embraced the whole of the British Isles and 
other lands now submerged below the sea. If, as has been 
advocated by Mr. James Geikie, the mingling together of 
the bones of the northern and southern mammals was 
not due to the range of their summer and winter migrations 
overlapping, but to the remains belonging to widely different 
periods having been afterwards mixed together,]: it is inex- 
plicable that mollusks denoting a warmer climate should 
not have accompanied the southern mammals in the valley 
of the Main. On the other hand, such a fadt is fully ex- 
plained if the winters were colder and the summers warmer, 
for the slow crawling mollusks could not retreat southward 
on the approach of winter along with the southern mammals, 
* Geological Magazine, 1874, p. 220. 
f See Cave Hunting, p. 397. 
X Great Ice Age, p. 467. 
