TRANSACTIONS OF SECTION C. 491 
(4) Tae Masrer-Divisions oF THE TERTIARY PERIOD. 
The master-divisions of the Tertiary Period may be defined by the following 
characters so far as relates to the mammalia :— 
a. The Eocene Age, or that in which the placental mammals now on the earth 
were represented by allied forms belonging to existing families and orders. No 
living genera of placental mammals were present either in the Old or the New 
World. For example, the order Primates, to which man belongs, is represented 
by lemur-like creatures (adapis) in the Upper Eocenes of Europe, and in the 
Lower Middle and Upper Eocenes of the United States. The Kocene carnivores 
present close affinities with the marsupials, and one living marsupial genus (didel- 
phys), opossum, haunted the Eocene forests of Europe. 
b. The Meiocene Age.—In the Meiocene Age we meet with living genera for 
the first time, such as rhinoceros, cervus, antelope, tapir, hog, cat, hyzena, and 
others. The Primates are represented by higher forms than before, by the simiade, 
or true apes, both in the Old and New Worlds. It is also worthy of note that in 
the Lower Meiocene Period in Europe marsupials were still present. The 
opossums still lingered in the forests, and the marsupial ancestry of the carnivores 
still asserted itself in the singular combination of characters offered by the 
hyenodon. 
The term Oligocene, originally invented by Professor Beyrich in 1856, and 
recently adopted in Britain by Professor Judd, embraces the Upper Eocenes and 
the Lower Meiocenes. It appears to me an unnecessary subdivision and to be 
ineapable of definition by its fossil contents from the Upper Eocene and Lower 
Meiocene strata. It includes such characteristic forms as the Upper Eocene 
paleotherium and the Meiocene deinothertwm. 
c. The Pleiocene Age—In the next or Pleiocene Age the living genera are 
abundant, and living mammalian species appear, such as the hippopotamus, in a 
fauna mainly characterised by extinct species of mammalia. 
d. The Pleistocene Age.—In the Pleistocene Age living species of placental 
mammals predominated greatly over the extinct, and caye- and river-drift man 
appears. In this age the mammal fauna of the whole world reached its present 
phase of development—in Europe the European, in India the Indian, and in 
North and South America the types now found in those parts of the world. In 
Australia also the marsupials present the same stage of development, and the living 
marsupials are more numerous than the extinct. The term ‘Glacial,’ sometimes 
used as the equivalent of Pleistocene, is merely of local application, and applies 
only to those regions in which the traces of glaciers and icebergs occur, where 
glaciers and icebergs are no longer to be found. ‘ Quaternary ’ is open to the grave 
objection mentioned above, that it implies a break in life which has no existence. 
e. The Prehistoric Period.—The vegetable and animal kingdom had arrived at 
their present stage of specialisation at the close of the Pleistocene Age, and there- 
fore the series of events from that age down to the present time must be locked at 
from a point of view other than that offered by the evolution of the mammalia. 
The point of view which seems to me the best is that offered by history, and 
they may be divided into the prehistoric and the historic. The prehistoric period 
is that in which the domestic animals and cultivated fruits appear. Man is 
abundant, and in the neolithic bronze and iron stages of culture. ; 
f. The Historic Period, or that embraced by the written records, varies in 
different countries. 
These definitions are, so far as the author knows, no mere parochial definitions 
applicable to a limited area, but apply to the series of events in the Tertiary Period 
over the whole world. They are the result of an inquiry which he undertook some 
twenty years ago at the request of his late friend John Richard Green, to see 
whether the series of events recorded in the Tertiary strata could be brought into 
relation with those recorded by history. 
4, Report on the Exploration of Caves in the Carboniferous Limestone in tho 
South of Ireland.—See Reports, p. 132 
