who regard the marine faunas as much the most reliable indices of geological age.

During geological time the open sea has certainly afforded far greater uniformity of conditions for the existence and evolution of the different forms of life which it has contained than the land and fresh waters have done. Therefore, it is reasonable to conclude that, as a rule, the progress and ratio of the differentiation, evolution, and decadence among marine forms have been more uniform throughout geological time, and over greater areas, than has been the case with continental life. While, as we have seen. the ratio of evolution and decadence of marine types among themselves has not been so uniform as it has been assumed to have been by the European paleontological standard, such a ratio for the continental forms of life has often not only an extraordinary want of uniformity among themselves, but it is often at great variance with that of marine life.

Now it seems to me that the absence of a uniform ratio of evolution and decadence between marine, fresh-water, and land faunas and land floras, respectively, is just what we ought to expect when we consider the great variety of character of the various forms of life involved, and the great diversity of physical conditions under which they have existed. All that we yet know of ancient continental life points to the conclusion that the evolution of its various forms has been subject to frequent accelerations and retardations; and that, as a rule, they have been more subject to abrupt extinction than marine forms have. It is true, however, that some of the types among the continental faunas and floras which are now living have come down to us from very ancient times. It is also evident that a uniform rate of evolution of similar forms of continental life did not obtain in all parts of the world during the respective geological periods. An illustration of my meaning in this respect is afforded by our Cretaceous dicotyledonous flora already referred to. In America that flora had reached the European Tertiary stage long before the close of the Cretaceous period.

The instances which I have mentioned, besides many others which might be referred to, show that the confidence with which many paleontologists have decided upon the question of the synchronism of formations in widely separated portions of the earth. some of which are at most only one or two hundred feet in thickness, is quite unjustifiable.

I would gladly end here my arraignment of the unwarrantable positions which paleontologists have hitherto assumed, but I have yet to refer to others, especially to the custom of deciding upon the homotaxial relationship, or so-called equivalency, of formations upon insufficient evidence. Before the student of living animals and plants is prepared to decide in a satisfactory manner upon the forms which he is investigating, he requires not only a series of perfect specimens of his species, but also all that can be known of its anatomy and physiology, its habits and habitat, its associated forms, and its specific and generic relations. On the contrary, the paleontologist, as is well known, is confined to the study of such of the hard or skeletal parts of animals as may have escaped destruction by decomposition or other means; and the imprints or fragments of plants, mainly leaves.

One cannot cease to wonder at and admire the large amount of real knowledge which has been gained by the study of even such imperfect material as this. In fact, all that we know of the ancient life of the earth has been derived from this source; and by means of comparisons with related living forms we are often able, by the aid of a perfectly legitimate use of the imagination, to restore to a large extent the faunas and floras of long past geological periods. Encouraged by this success, and urged by the necessities of geology, paleontologists have assumed not only to decide upon the specific and generic identity of the forms represented by such imperfect material, but also to base upon it generalizations of the greatest importance in both geology and biology.

Every investigator knows how small a clue will sometimes lead to the unravelling of obscure problems in scientific research, and no one has more frequent occasion to give earnest attention to such clues than the working paleontologist. Indeed, some of his best results would often have escaped him if such clues had been disregarded. Such a use of even the most insignificant facts is perfectly legitimate; but I wish to refer especially to the practice which has prevailed of publishing what are ostensibly conclusions which have been reached from legitimate investigation, when in reality they are at best little more than mere surmises. I will give a couple of instances of this kind to illustrate my meaning.

In California and Western Nevada, where the country is mountainous and the rocks are much displaced and more or less altered, several isolated and limited exposures of strata have been found which contained a few fossil shells. At some of the localities half a dozen species are represented, but at some only one or two species. Most of these specimens are too imperfect to serve as the basis of even a satisfactory specific description; and none of the types presumably represented by them are of such a character as to give reasonable assurance of even homotaxial relationship with those of any European formation.

The most that can be said of this meagre fauna is that it is probably of Mesozoic age. And yet the equivalency of these rocks with the Jurassic of Europe has been confidently asserted, and broad generalizations have been based upon that assumption as to the age of mountain uplifts and other great geological

events.

Again, there is in the western portion of the United States domain a formation which all geologists and paleontologists have agreed in referring to the Jurassic period. It is true that its invertebrate fauna is not full enough to afford entirely satisfactory evidence on this point, but the rich vertebrate fauna which

Professor Marsh has published from that formation has been accepted as conclusive. Furthermore, the position of the formation in relation to those which underlie and overlie it is confirmatory of the received opinion as to its Jurassic age. Notwithstanding this weight of evidence in the direction indicated, the paleontologist of the Canadian Geological Survey has, upon what I believe to be the mistaken identification of a comparatively small collection of imperfect and uncharacteristic fossil shells, referred the formation bodily to the Middle Cretaceous. When such a circumstance as this is possible it is certainly time we should examine well the grounds of our conclusions before we publish them to the world or base other results of our labors upon them.

While belief in the general applicability to all parts of the world of the chronological scale now in common use will probably never be seriously shaken, it is plain that we must abandon the idea that formations in widely separated parts of the world were necessarily synchronous in their origin because certain portions of their faunas or floras are similar. The custom has been to recognize a complete chronological scheme of the formations. of universal application, as already established, and to prosecute the geology of every part of the earth with the express view of making it conform to that scheme. But I submit that the geology of each of the large divisions of the earth ought to be studied independently, and untrammelled by preconceived notions of necessary conformity to a foreign standard. In my opinion, the time has not yet come for the construction of a complete and detailed chronological scale for the whole earth, and that it will not have fully arrived until the whole earth shall have been carefully studied.

If geology were studied in the different divisions of the earth with the ideas in view which I have indicated, its prosecution would be relieved of much useless labor, as well as freed from a

large proportion of the now prevailing liability to error. I do not wish to be understood as trying to discourage comparisons of the geology of different parts of the earth with each other. On the contrary, this ought constantly to be done; but what I wish to insist upon is that the study of each separate division of the earth should not be trammelled by a standard erected for another.

I have shown that the study of geology and paleontology has always been interdependent; but among certain geologists and paleontologists, respectively, there has been manifested a disposition to pursue the study of each branch separately, if not independently. A large part of the paleontological work which has been published has been done by men who have made no systematic study of field geology, or none in connection with their paleontological work. Much of their work has evidently been done in the belief that the paleontologist can sit in his study and fix with precision the geological horizons and the order of succession of the formations from which every collection submitted to him may come. If a difference of opinion in this respect has arisen between the field geologist and the paleontologist, each has contended for the truth of his own position, and each has often been shown to be in error.

It is therefore evident that the field geologist and paleontologist must work in concert. Indeed, the field geologist who ignores the use of fossils, as some have affected to do. is sure to burthen science with the results of worthless work; and the paleontologist who does not go to the field and study there the formations from which his fossils have been obtained is sure to produce results of work which will be worthy of the condemnation of both geologists and biologists.

But I am confident that there is a better day near at hand for the science to which so many able men have devoted their lives; and that the evils to which I have called your attention are already