when found as fossils. Limited in geographical distribution 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 difficulties of determination occur, and these are perhaps greater than at first sight appears, for it by

no

means follows that, because we are unable to differentiate, 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 animal to deal with, we should regard them as identical, or even as so closely allied that they 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 localities of forms such as these that doubtful correlations are sometimes

vehemently asserted. Doubtless they are, at times, all we have to go upon, but in such a case a suspension of judgment is oftener the wiser course.

Ag

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 forms a few stragglers from ancient times persist, like Trigonia 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 increase in our knowledge has banished from all but a few belated popular works. a matter of fact, our seas are no richer in "living fossils " than those of other parts of the world. Our Cestracion is surpassed by Chlamydoselache and Heptanchus, and Trigonia is matched by Pholadomya and Nautilus. Our marine fauna is as highly specialised, and, so to speak, as recent, as that of any other region; and had it and our fossils been investigated 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 AND 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 temperature may have been more uniform over the surface of

the globe, and there may have been a closer approach to uniformity in the plants and animals of widely separated localities, but it may be safely said that identity never existed. Here in Australia we are at the Antipodes of all the well-worked formations of the world, and more and more clearly, as detailed work is pushed on, do the differences appear. At first it was customary to ascribe almost all our fossils, from Palæozoic to Terciary, to European forms; but, with the growth of collections, the distinctions between allied forms are being elucidated.

46

M'Coy, in 1861 (M'Coy, '61, p. 162), says--" Confining ourselves to the details, now first made known, of the contents of the graptolite beds, we have the astonishing fact of the specific identity of the marine fauna over the whole world during the most ancient palæozoic period." And, further on, We can point now for the first time to the marvellous fact of the specific identity of the inhabitants of the seas of the most widely distant points of the northern and southern hemispheres during this second great geological epoch of the zoological history of the earth" [i.e., the Upper Silurian of the Victorian Survey.] In the same essay, in a less sweeping way, he extends this view so as to comprise the more recent periods. In this connection it must be remembered that M'Coy arrived at this conclusion when he was fresh from the study of the Paleozoic fossils of Britain, and possibly, had he waited till' more perfect material was obtained. he would not have put forward this idea, which, however, he never relinquished.

De Koninck (de Koninck, '98, p. 2) says M'Coy "has not hesitated to admit the general specific identity of the marine fauna of the two hemispheres in the early times of the Paleozoic Era. My own observations enable me to confirm" this. "I may add, as well, that I arrive at the same conclusions, as far as the Devonian and Carboniferous systems are concerned." However, it cannot be said that subsequent work has confirmed this; and Etheridge points out (Etheridge, '91, p. 125)-"No service can be rendered to Australian stratigraphical geology by the definite reference of any of its fossils to European species, unless on the clearest possible evidence." The Clarke, collection, on which de Koninck founded his generalisation, was destroyed by fire, so that we have no means of checking his records in detail; but Etheridge has suggested, in the descriptions of many new species, gathered from the same localities as Clarke's fossils, that the supposed identities were frequently mere

resemblances, while in the case of the corals the resemblances were quite superficial, and the Australian species were generically, or even ordinarily, distinct. (Etheridge in de Koninck, '98.) Specific identities do undoubtedly occur, especially among the fossils of the older formations, but they are not in overwhelming numbers.

A. C. Seward (Seward, '00, p. 303) says "The _comparison of the English plants with the Upper Gondwana flora of India, and with Australian floras of corresponding geological position, has confirmed me in the opinion that the differences between the Mesozoic vegetation of the Northern and Southern Hemispheres have been greatly exaggerated. Geographical separation of fossil species frequently leads to an unnecessary amount of specific distinction in the naming and determination of plants . . In Jurassic times there was, no doubt, a much greater uniformity in the vegetation of the world than exists at the present day. A closer analysis of the Gondwana floras and a more detailed comparison with those of the Northern Hemisphere may enable us to recognise well-defined distinguishing features suggestive of botanical provinces, such as existed in the Lower Gondwana period; but this is a matter for subsequent treatment."

The belief of Baron von Ettingshausen in a universal Tertiary flora is well known (von Ettingshausen, '83), and he derived much support of his view from his investigations of the Tertiary fossil plants of Australia. It must, however, now be generally conceded that Mr. Henry Deane (Deane, '96, '97, '00, '01) has shown that the whole idea is a mistaken one, and rests on the comparison of our fossils with European recent forms, instead of with those now actually growing in Australia. Our Tertiary flora, in fact, proves to have been as typically Australian as anything we have at the present day.

There remains yet another asserted case of a cosmopolitan fauna which we may consider, and this is the one suggested by Murray and advocated by Pfeffer, in order to explain Bipolarity in the Distribution of Animals.

THE BIPOLAR THEORY.

It is stated that there are large numbers of animals of various groups present in the seas of high northern and southern latitudes which are absent in the intervening tropical regions, and this is explained by the supposition of a universal early Tertiary fauna. But opinions differ both as

to the existence of the similarity and as to its explanation. In a recent summary of the evidence in favour of the theory, Miss E. M. Pratt (Pratt, '01) says that Pfeffer, Murray, Selenka, De Guerne, Fischer, Shipley, Théel, Ehlers, I. C. Thompson, and herself, who have all worked on material from the far South, are believers in the resemblances. On the other side, we have D'Arcy Thompson, Herdman, Ludwig, Chun, and Ortmann, who also speak from personal knowledge, and are just as strong in their disbelief of the similarity of the two faunas.

The evidence marshalled by the supporters of the idea asto the present distribution of the fauna is explicit, and must be weighed and valued by experts in the various groups; but there seems to be no doubt that there are certain animals either species or genera, or even higher groups which are present in both Arctic and Antarctic seas, and appear to be absent from the intervening ones. Even if there be no specific agreement in the case, still the resemblances in some cases are undoubted. But even if we take the statements as to the great similarity of the two polar faunas as correct, we have yet to consider the theory which would explain the asserted facts.

Sir John Murray (Murray, '95) gives a laborious summary of the question. Taking the Kerguelen region as typical, he finds about 530 animals are known. Of these 45 occur in the North Atlantic, 11 in the North Pacific, but only 18 in the tropical Atlantic, and 22 in the tropical Pacific. He concludes that it may "be assumed that the identical species now found living towards both poles, or their immediate ancestors, had a world-wide distribution, which involves a nearly uniform temperature throughout the whole body of ocean waters."

Perhaps the most trenchant article against the theory is that of D'Arcy Thompson (Thompson, '00), in which he discusses Murray's list in detail, and sums up by saying (l.c., p. 313) Many, if not most [of these], are dubious, even in the eyes of their first recorders--many others have too few characters for precise recognition." He also insists, with justice, as we shall see in the sequel, that we must dis criminate between those whose affinities appertain to the fauna of the North Pacific and of the North Atlantic res pectively. For the fauna of the North Pacific presents many unknown problems for us; but this we do know, that it contains in part a northern circumpolar fauna, and in part a fauna very distinct from that of the North Atlantic, and peculiarly linked to the fauna of the Southern Ocean."

Some of the forms he instances, from a circumpolar habitat in the Antarctic, seem to creep up to varying distances along the Western American coasts to the Galapagos, to California, and even to the northern islands of Japan.` Thompson would then have us believe, with Ortman (1) (Ortmann, '01. I am unable to refer to this paper, and quote from Miss Pratt's rendering of it) that what agreement there is is, in the main, due to migration along the western shores of America, from south to north, where cold currents lower the temperature of the tropical seas. The explanation. which at present concerns us is that given by Murray, and stated more strongly by (Pfeffer, '01, p. 311), and that is the theory of a uniform early Tertiary fauna. We must, says Pfeffer," accordingly expect to find in the oldest and earlier middle Tertiary a large number of species identically occurring in the Northern and Southern Hemispheres, for instance, in our own region, and in South [sic] Australia. If we simply compare the lists which have been drawn up, this certainly does not seem to have been the case; but if we take account also of the remarks made by the authors, we find that there is a large number of species closely allied to, and difficult to distinguish from those in the Antipodes of a similar age. When, further, we recall that the palæontologists of different countries have very often named their species with little or no reference to the works of their colleagues, we have to admit that circumpolarity of the earlier Tertiary faunas was so marked that it extended not only to the greater majority of genera, but in a great many cases (whose number future studies will probably increase), even to species. And thus it is certain that the early Tertiary fauna had an approximately similar uniform expression or representation throughout the whole region of its development." Further on he says "The faunas of higher latitudes represent coeval relics of the almost uniformly developed and almost uniformly distributed early Tertiary faunas, as they have been evolved under the influence of the cooling of the climate by a process of separating out and selecting. The similarity of the operating causes secured that the same components of the old fauna remained behind in both north and south, and thus has arisen the great and well-marked similarity of the two faunas."

The

This is an extremely clever case of special pleading, and is, in my opinion, absolutely without justification. fauna of our older Tertiaries has been investigated chiefly by men familiar with that of Europe, and in some cases, anxious, apparently, to identify it with that of European