21 
conditions. Turtles and crocodiles have left their remains behind 
in the London Clay, and beside the Odontopteryx already 
mentioned there were herons, kingfishers, gulls, vultures, and 
other large birds. All the species, however, are now extinct, and 
there are no signs of man nor of any of the mammalia most nearly 
related to him in structure. And Britain was not yet an island. - 
During the next period, the Oligocene, upheaval still went on, 
more land was exposed, and a connection was made across the 
Strait of Dover. All western Europe participated in this move- 
ment, so that there was free communication with Africa in more 
than one place. Across these pathways came multitudes of new 
genera and species from the south; Cornwall, Devon, and the 
south-east of Ireland were mountainous districts with no separation 
between them and France beyond the valley of a large river. ‘The 
greater part of the North Sea became dry, driving the waters 
southward, but there was no connection with the Atlantic. During 
this upheaval many lakes must have been left behind, and one 
interesting set of lacustrine deposits has been preserved in Devon- 
shire near Bovey Tracey. It appears to have been a lake at least 
300 feet deep and covering about five and twenty square miles, fed 
by the rivers Teign and Bovey, then quite independent of each 
other. Dartmoor stood there as now, but looking down on this 
lake, whose waters reflected the forms of snch trees as the 
Sequoia, evergreen oaks, figs, cinnamon, laurels, vines, and gum- 
trees, while large clusters of water lilies floated on the surface. 
Everything betokened a warm climate. 
Still the elevatory movement continued, and through all the 
Miocené period, Great Britain and Ireland appear to have remained 
dry land, as no deposits of this age, or any signs of them are to be 
found here; we were still part of a large continent, European on 
the east, and stretching to Greenland and America on the west. 
The North Sea formed a vast Miocene plain, watered by rivers from 
the Scandinavian mountains, from Holland and Belgium, and on the 
opposite side by those from Great Britain. There is at the present 
time off the south-west coast of Norway a submarine valley 200 
feet below the sea-bed; possibly this is the valley of a large 
Miocene river, The Miocene Age was a long one, as is shown by 
the great changes which took place in the animals and plants. 
- Large areas of chalk and Eocene deposits were removed by the 
rains, rivers and frosts of the time; the great oolitic escarpment 
stretching from the Cotswold Hills to the N.E. was formed ; the 
Thames commenced to carve out its present valley, though 
probably only as a tributary of the Rhine; and the dome of the 
Weald was lifted up, and most of the chalk cleared off it. 
