Ve 
166 PROCEEDINGS OF SECTION C. 
when found as fossils. Limited in geographical distribu- 
tion and in geological range. they are of considerable value 
to the geologist in the study of limited areas; but it is the 
less specialised forms to which we must turn in attempting 
to correlate strata widely separated in space. It is just 
here, however, among these generalised forms, that difficul- 
ties of determimation occur, and these are perhaps 
greater than at first sight appears, for it by no 
means follows that, because we are unable to differen- 
tiate, for instance, an Australian Tertiary Limopsis from 
L. aurita of Europe, or a Saxicava from S. arctica, that, if we 
found them recent, and had the whole anima! to deal with, 
we should regard them as identical, or even as so closely 
ailied thai chey are only separated by trivialities. and are 
-directly sprung from the self-same stock. Yet it is on such 
superficial likenesses that broad generalisations are apt to 
be built, on the occurrence in widely-separated localiues of 
forms such as these that doubtful correlations are sometimes 
vehemently asserted. Doubtless they are, at times, all we 
have co go upon,.but in such a case a ramen of judg- 
ment is oftener the wiser course. 
The long-continued isolation of Australia has preserved 
“archaic types among its terrestrial inhabitants, and there 
is no need to specially draw attention to them. Similarly, 
among the marine foyams a few stragglers from ancient times 
persist, like Z'r7gonia among molluscs and Cestracion among 
fishes. Thus there sprang into existence that strange theory 
that in Australia we were, so to speak. still living in the 
' Jurassic period—a theory which imcrease in our knowledge 
has banished from all but a few belated popular works. As 
a matter of fact, our seas are no ricber in “ living fossils ”’ 
than those of other parts of the world. Our Cestracion is 
surpassed by Chiamydoselache and Heptanchus, andTrigonia 
is matched by Pholadomya and Vautdus. Ourmarine fauna 
is as highly specialised. and, so to speak, as recent. as that 
of any other region; and had it and our fossils been investi- 
gated before those of the Northern Hemisphere, as much 
attention would have been drawn to northern abnormalities 
as has been directed to southern ones. “Orthodoxy is my 
‘doxy,’ heterodoxy is the other man’s doxy.” 
UNIVERSAL FLoRAS snp Faunas. 
The theory of universal floras and faunas at various periods 
in the past-has been supported by many, and arrived at on: 
several grounds. Possibly in past times conditions of tem- 
‘perature may have been more uriform over the surface of 
