490 -- REPORT—1883. 
numerous in the Keuper sandstone, which was frequently fractured during subsi- 
dence into a depression, the pebble-beds are very little faulted. A few days ago, 
when under the Mersey, I did not find a single fault either in the tunnel or in the 
heading beneath. 
3. The Master-Divisions of the Tertiary Period. 
By Professor W. Boyp Dawkins, F’.R.S, 
(1) Inrropvction, 
The classification of Tertiary rocks sketched out some fifty years ago, and since 
then altered in no important degree, is out of harmony with our present knowledge, 
and the definitions of the series of events which took place in it has been greatly 
modified by the progress of discovery in various parts of the world. The terms 
Eocene, Meiocene, and Pleiocene no longer express the idea of percentages of living 
species of fossil mollusca upon which they were based, and ‘ Post-tertiary, Quater- 
nary, and ‘ Recent’ are founded on the assumed existence of a great break com- 
parable to that separating the Secondary from the Primary or Tertiary Periods, 
which has long ago been given up. In 1880! the author proposed a classification 
of the Tertiary Period in Europe by an appeal to the land-mammalia, and since 
that time his definitions have been found to apply equally well to the Tertiaries of 
Asia and the Americas, and to the later Tertiaries of Australia. He therefore 
presents the following outline to the members of the British Association. 
(2) THe PRINCIPLE OF CLASSIFICATION. 
The forms of life in the rocks have changed at a very variable rate, and in direct 
proportion to their complexity of organisation, the lower and simpler having an 
enormous range in the rocks, while the higher and more complex have a much 
narrower range, and have been more easily affected by changes in the environment. 
The carboniferous conifers, for example, do not differ profoundly from living forms, 
while the carboniferous labyrinthodons have left no representatives behind them. 
At the beginning of the Tertiary Period the whole of the vegetable kingdom, and 
with but some few exceptions the invertebrata in the animal kingdom, had 
arrived at the stage of evolution which they now present. The fishes, amphibians, 
and reptiles belong to well-recognised types in existing nature, and the birds had 
left behind the ancestral characters which allied them so closely to the reptiles in 
the Secondary Period—the long tail, and the armature of teeth in their beaks—and 
belong to living orders. 
The mammalia, on the other hand, feebly represented in the Secondary Period 
by small marsupial forms, appear in force in the early Tertiary beds, and were, as 
Prof. Gaudry happily terms it, ‘en pleine évolution’ in the early divisions of the 
Tertiary strata—the Eo-, Meio-, and Pleio-cene Ages—and have changed with suffi- 
cient swiftness to allow of their being used to mark the hour on the geological 
clock in different parts of the world. 
(3) Tue Tertiary PERIOD INCLUDES OUR OWN TIME. 
Nor can there be any doubt as to the definition of the series of events included 
under the term Tertiary. It begins with the appearance of the placentalmammalia, 
and it must include our own time if it be looked at from the same biological point of 
view as the Primary or Secondary groups. With some few exceptions the whole of 
the plants and animals now alive were living in the Pleiocene and Pleistocene ages, 
and therefore there is no break of sufficient importance to justify the use of the 
terms ‘ post-Tertiary ’ or ‘Quaternary’ for the newer divisions. These exceptions 
are probably due merely to the accident of their non-discovery in the Pleiocene and 
Pleistocene strata. 
' Quarterly Journal of the Geological Society, London, Aug. 1880. See also my 
work on Larly Man in Britain, 1880. 
—_ 
