PRESIDENT’S ADDRESS. 173 
It is beside our present purpose to deal at length with this 
well-worn theme, and the result may be well expressed in the 
words of Seward (Seward, °97. p. 194)—“‘ From some cause, 
then, it would appear that the Paleozoic vegetation, which 
in Lower Carboniferous times had a more or less world-wide 
distribution, was replaced in the south by a new set of 
plants, while in the Northern Hemisphere the older forms 
continued to fiourish til] the end of the Permian epoch, and 
were then superseded by a flora of a newer facies.” 
One effect of the Glossopteris controversy has been to 
shake, perhaps unduly, our confidence in the evidence of 
plants, and of terrestrial forms generally, as indices of age, 
and we are told that the marine fauna is the only reliabie 
test that we have, that the terrestrial fauna and flora which 
originated in Gondwana Land could not migrate north 
on account of a marine barrier. and when this marine bar- 
rier was bridged then an incursion northwards took place. 
Is there no possibility, it may be asked, of a land barrier 
delaying the spread of marine forms in a similar way ? 
It has long been customary to refer to our Australian 
formations by the names used by European geologists, and, 
broadly speaking, we are, no doubt, justified in such a 
course; and yet difficulties at times arise from the apparent 
mingling of the faunas of two distinct periods. The usual 
solutioa of the difficulty is to accept the idea that some of 
our beds are consequently intermediate in age; that they 
represent the lapse of time indicated by the unconformities 
which so definitely delimit the periods in the Northern 
Hemisphere; and-thus have arisen the terms Cretaceo- 
Eocene, Permo-Carboniferous. Siluro-Devonian, and Cambro- 
Silurian. These terms are used to designate straca that, 
like Janus, are two-faced. The fact that they are inter- 
mediate by no means follows from the premises, for we 
must bear in mind the possibility of a somewhac different 
range in the Antipodes of certain forms of life. This trans- 
gression of genera has been proved in the case of some of 
the Lower Ordovician graptolites of Victoria, where those 
of Lancefield show a mingling of Cambrian and Ordovician 
forms.. 
In his presidential address to this Association, in 1893, 
Professor Tate said. in speaking of Australia (Tate, 794, p. 
34)—“ The limits of the Silurian and Devonian, and of the 
Devonian and Carboniferous, seem so ill-defined that it is 
questionable if the middle term exists, as viewed from a 
European or North American standpoint. Then we have 
the paleontological overlap of the Paleozoic and Mesozoic 
