yS The Loess of the Rhine and the Danube . [January, 
species, being at present rare in the basin of the Rhine, but 
abounding much farther north, in Scandinavia and Northern 
Russia. The little Pupa muscorum , which nearly everywhere 
accompanies the last mollusk in the loess, ranges through- 
out Europe from Iceland and Lapland to the Mediterranean. 
The minute Helix pulchella , which I have also found very 
generally distributed in the loess, has a still wider range, 
being found from Siberia to Corsica, throughout Canada, 
and even in the Azores. Helix hispida , a common loess 
shell, and H. sericea, which replaces it near Wurzberg, range 
from Siberia to the Mediterranean. 
The fauna of the loess is the same in the basins of the 
Danube and the Rhine, and in Southern Russia ; it belongs 
entirely to the period of the mammoth and the woolly rhi- 
noceros. Neither the highest nor the lowest patches of 
it contain the remains of any other fauna. It is one fitted 
to endure a cold climate. It is the culmination of a series 
showing a gradual refrigeration of the northern hemisphere 
from early tertiary times. The tropical forms of the Eocene 
strata are succeeded by the semi-tropical ones of the Mio- 
cene : these by the more temperate species of the Pliocene ; 
then comes in the fauna of the Mosbach gravels, the Diirn- 
ten lignites, the Cromer Forest and the oldest Thames 
brick-earths, when palaeolithic man first appears on the 
scene in Northern Europe, and when the mean temperature 
was probably about the same as now, though the winters were 
colder and the summers warmer. Then, distinctly super- 
imposed upon the Mosbach sands and gravels, comes the 
last fauna of all before the present, — that which is found in 
the newer gravels and the loess resting on them, — the fauna 
of the mammoth and the woolly rhinoceros, along with 
which we find the latest remains of palaeolithic man in 
Northern Europe. That that fauna belongs to the Glacial 
period is evidenced not only by the fadt that it is composed 
of species best able to withstand extreme cold, but that in 
the valley of the Danube large boulders occur in the loess 
that must have been transported on icebergs whilst it was. 
being deposited. 
No more arCtic fauna is known in the basins of the Danube 
and the Rhine than that of the loess. Above it, as elsewhere, 
at this stage, there is a great break in the succession of life ; 
the mammoth, the woolly rhinoceros, and palaeolithic man 
disappear ; and after that interruption the next forms that 
appear are those of the recent period. Neolithic man now 
takes possession of the land, and with him comes a number 
of animals that still remain with us, with the exception of 
