Reviews—Prestwich on Valley-Deposits. 23 
but at Hoxne, the Oak, Yew, Fir, and possibly Bilberry, have been 
found. 
Taken together, the organic remains, though not affording decisive 
evidence of the character of the climate at the time of the deposit of 
the high-level gravels, show a balance in favour of the probability 
of a climate severer than at present in the same latitude, though 
not of extreme rigour. It must have been a climate in which the 
Oak, Yew, and Fir could thrive ; where the Reindeer lived ; and where 
the Deer, Horse, and Ox abounded; but where the rivers were subject 
to periodical floods; where they froze, so as to be able to transport 
the large boulders already mentioned ; and where the ice ‘ packed’ 
in sufficient quantities to produce contortions in the beds, such as 
already described ; for in the same way as the contortions in the clay 
cliffs of Norfolk have by Mr. Trimmer and Sir C. Lyell been attri- 
buted to the grounding of icebergs, so is Mr. Prestwich disposed to 
attribute to a somewhat like action of the river-ice, on a small scale, 
the analogous structure exhibited by the St. Acheul and other high- 
level gravels. 
Turning now to the low-level gravels, we find in them an in- 
crease in the number of species of land and fresh-water molluscs, 
which are here 52. This group also maintains a slightly northern 
aspect; as, out of the 52, 42 are now living in Sweden, and 37 in 
Finland. It comprises, therefore, nearly one half of the Finnish 
species; whereas only one fifth of the Lombardic species, or 38 out 
of 198, occur in the beds. At Menchecourt, near Abbeville, some 
marine and estuarine shells occur; among them, Littorina squalida, 
which has now retreated to the coast of Norway, and Tellina 
Balthica, which is a northern variety. Of the fresh-water shells, 
Cyrena fluminalis deserves especial mention. It is now only found 
in the Nile and in mountain-streams of Central Asia—a range 
presenting great extremes of climate. Among the mammalia we 
now find Hippotamus major and Felis spelea, which at first sight 
seem to militate against the theory of the climate of the period 
having been severe; but, as Mr. Prestwich observes, ‘like its con- 
geners, the Elephant and Rhinoceros, this Hippotamus belongs to an 
extinct species, and it becomes a question whether, like them, it may 
not have been adapted to endure the rigours of a severer climate than 
the living species of these genera can now endure.’ As to the Tiger, 
there is at the present day a species common on the lower Amoor, 
where the river is frozen five months in the year. The flora of the 
‘low-level’ period is confined to a solitary specimen of Chara; so 
that the premises from which to draw conclusions as to climate are 
limited. Still, on the whole, Mr. Prestwich considers that the evi- 
dence is in favour of its having been rather less severe than that of 
the previous high-level-gravel period. 
In a former paper he has shown that these high-level gravels are 
in their turn newer than the Boulder-clay of England and the period 
of extreme cold marked by the great extension of the European 
glaciers ; and he here goes on to show how well the phenomena 
observable in the valley-gravels agree with a climate in which the 
