OLDEK PLIOCENE. 
69 
of time. These strata are therefore classed provisionally with 
those of Lenham and St. Erth, and with the Coralline Crag; 
the correlation of the English and foreign Pliocene deposits will, 
however, be again alluded to in the chapters on the Red Crag and 
on foreign equivalents (pp. 98, 99, 222, 223). 
In the foregoing description of the different Older Pliocene 
deposits, especial attention has been drawn to the height above the 
sea-level at which each is now found, and to the depth of water 
indicated by the included fossils. The data show that instead of 
the faunal zones varying according to the varying height of the 
beds above the sea level, or depth below the sea, the Older Pliocene 
beds of St. Erth and I^enham, the Coralline Crag, and the Diestian 
of Antwerp and of Utrecht all point to very similar bathimetric 
conditions, and were all probably laid down in depths ranging 
between 30 .‘ind 50 fathoms. If the movements which have 
elevated the Lenham deposits 620 feet above the sea had been 
uniform in amount over the whole of the area dealt with in this 
Memoir we might expect to find evidence in some of the Older 
Pliocene strata of seas of considerable depth, and of a corre¬ 
sponding deep-water fauna. Taking Lenham as our starting 
point, with an indicated rise of 860 feet—obtained by adding the 
present elevation of the strata above the sea to the depth at 
which they were laid down—:we ought to find indications of a 
submergence to the extent of 840 feet (140 fathoms) in the 
Coralline Crag, and of 2,000 feet (330 fathoms) at Utrecht. 
A Pliocene fauna of over 300 fathoms would be most 
interesting to examine, but of such a fauna no trace has yet been 
detected anywhere in North-Western Europe. All the Older 
Pliocene dejoosits, though now occurring at such different levels, 
are shown by their included fossils to have been laid down in 
about the same depth of water. Though differing much in 
mineral composition at the various localities, they nevertheless 
agree as closely in regard to their fossils as the very different 
nature of the sea-bottoms would allow us to expect. The whole 
1,143 feet of Pliocene and Pleistocene beds at Utrecht consists 
of essentially shallow-water deposits, pointing to a continuous 
depression. In Holland subsidence apparently tends to affect the 
same area again and again. 
On the other hand, the question arises whether the elevation of 
the Weal den axis was still in progress during the Pliocene period. 
That the greater part of this enormous disturbance had been 
completed before that period seems proved by the absence of any 
Pliocene beds in the Hampshire or London basins, in the synclinal 
folds parallel with the Weald. There is, however, evidence of less 
violent movements of upheaval in the different levels at which 
Older Pliocene beds now occur, and it is probable that those 
geologists are right who maintain that the direction of the move¬ 
ments in areas of subsidence or elevation remains the same during 
long periods. Holland may thus have undergone continued, 
though probably intermittent, depression since the early part of 
the Pliocene period; so as to allow of the accumulation of a great 
